TerminologyThe Oxford English Dictionary defines a UFO as "An unidentified flying object; a ‘flying saucer’." The word was first used in print by Donald Keyhoe in 1953.
The acronym "UFO" was coined by Capt. Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short."  Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable flying object", and "flying saucer".
The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainer. Arnold timed the sighting and estimated the speed of discs to be over 1,000 mph. He described their movement like "a saucer skipped across water". The newspaper reporters then invented the "flying saucer". (see Kenneth Arnold UFO sighting for details).
In popular usage the term UFO came to sometimes be used to refer to alien spacecraft. and because of the public and media ridicule sometimes associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP)or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena or NARCAP.
The equivalent acronym for UFO in Spanish, Portuguese, French, and Italian is OVNI (Objeto Volador No Identificado, Objeto Voador Não Identificado, Objet volant non identifié or Oggetto Volante Non Identificato), pronounced as one word (ov-nee).
StudiesStudies have established that the majority of UFO observations are misidentified conventional objects or natural phenomena—most commonly aircraft, balloons, noctilucent clouds, nacreous clouds, or astronomical objects such as meteors or bright planets with a small percentage even being hoaxes. After excluding incorrect reports, however, most investigators have acknowledged that between 5% and 20% of reported sightings remain unexplained, and therefore can be classified as unidentified in the strictest sense. Many reports have been made by such trained observers as pilots, police, and the military; some have involved simultaneous radar tracking and visual accounts. Proponents of the extraterrestrial hypothesis suggest that these unexplained reports are of alien spacecraft, though various other hypotheses have been proposed.
While UFOs have been the subject of extensive investigation by various governments and although some scientists support the extraterrestrial hypothesis, few scientific papers about UFOs have been published in peer-reviewed journals. There has been some debate in the scientific community about whether any scientific investigation into UFO sightings is warranted.
The void left by the lack of institutional scientific study has given rise to independent researchers and groups, including NICAP (the National Investigations Committee on Aerial Phenomena) in the mid-1900s and, more recently, MUFON (Mutual UFO Network)  and CUFOS (Center for UFO Studies). The term "Ufology" is used to describe the collective efforts of those who study reports and associated evidence of unidentified flying objects. According to MUFON, as of 2011 the number of UFO reports to their worldwide offices has increased by 67% from the previous three years and now averages around 500 reported sightings per month.
UFOs have become a relevant theme in modern culture, and the social phenomena have been the subject of academic research in sociology and psychology.
Early historyUnexplained aerial observations have been reported throughout history. Some were undoubtedly astronomical in nature: comets, bright meteors, one or more of the five planets that can be seen with the naked eye, planetary conjunctions, or atmospheric optical phenomena such as parhelia and lenticular clouds. An example is Halley's Comet, which was recorded first by Chinese astronomers in 240 B.C. and possibly as early as 467 B.C. Such sightings throughout history often were treated as supernatural portents, angels, or other religious omens. Some current-day UFO researchers have noticed similarities between some religious symbols in medieval paintings and UFO reports though the canonical and symbolic character of such images is documented by art historians placing more conventional religious interpretations on such images.
- On January 25, 1878, The Denison Daily News noted that John Martin, a local farmer, had reported seeing a large, dark, circular object resembling a balloon flying "at wonderful speed." Martin, according to the newspaper account, said it appeared to be about the size of a saucer, the first known use of the word "saucer" in association with a UFO.
- On February 28, 1904, there was a sighting by three crew members on the USS Supply 300 miles west of San Francisco, reported by Lt. Frank Schofield, later to become Commander-in-Chief of the Pacific Battle Fleet. Schofield wrote of three bright red egg-shaped and circular objects flying in echelon formation that approached beneath the cloud layer, then changed course and "soared" above the clouds, departing directly away from the earth after two to three minutes. The largest had an apparent size of about six suns, he said.
- The three earliest known pilot UFO sightings, of 1,305 similar sitings cataloged by NARCAP, took place in 1916 and 1926. On January 31, 1916, a UK pilot near Rochford reported a row of lights, resembling lighted windows on a railway carriage, that rose and disappeared. In January 1926 a pilot reported six "flying manhole covers" between Wichita, Kansas, and Colorado Springs, Colorado. In late September 1926 an airmail pilot over Nevada said he had been forced to land by a huge, wingless, cylindrical object.
- On August 5, 1926, while traveling in the Humboldt Mountains of Tibet's Kokonor region, Russian explorer Nicholas Roerich reported, members of his expedition saw "something big and shiny reflecting the sun, like a huge oval moving at great speed. Crossing our camp the thing changed in its direction from south to southwest. And we saw how it disappeared in the intense blue sky. We even had time to take our field glasses and saw quite distinctly an oval form with shiny surface, one side of which was brilliant from the sun.” Another description by Roerich was of a "shiny body flying from north to south. Field glasses are at hand. It is a huge body. One side glows in the sun. It is oval in shape. Then it somehow turns in another direction and disappears in the southwest."
- In the Pacific and European theatres during World War II, "foo-fighters" (metallic spheres, balls of light and other shapes that followed aircraft) were reported and on occasion photographed by Allied and Axis pilots. Some proposed Allied explanations at the time included St. Elmo's Fire, the planet Venus, hallucinations from oxygen deprivation, or German secret weapons.
- On February 25, 1942, U.S. Army observers reported unidentified aircraft both visually and on radar over the Los Angeles, California, region. Antiaircraft artillery was fired at what were presumed to be Japanese planes. No readily apparent explanation was offered, though some officials dismissed the reports of aircraft as being triggered by anxieties over expected Japanese air attacks on California. However, Army Chief of Staff Gen. George C. Marshall and Secretary of War Henry Stimson insisted that real aircraft were involved. The incident later became known as the Battle of Los Angeles, or the West coast air raid.
- In 1946 more than 2,000 reports were collected, primarily by the Swedish military, of unidentified aerial objects over the Scandinavian nations, along with isolated reports from France, Portugal, Italy and Greece. The objects were referred to as "Russian hail" and later as "ghost rockets" because it was thought that the mysterious objects were possibly Russian tests of captured German V1 or V2 rockets. Although most were thought to be such natural phenomena as meteors, more than 200 were tracked on radar by the Swedish military and deemed to be "real physical objects." In a 1948 top secret document, Swedish authorities advised the USAF Europe that some of their investigators believed these craft to be extraterrestrial in origin.
InvestigationsUFOs have been subject to investigations over the years that varied widely in scope and scientific rigor. Governments or independent academics in the United States, Canada, the United Kingdom, Japan, Peru, France, Belgium, Sweden, Brazil, Chile, Uruguay, Mexico, Spain, and the Soviet Union are known to have investigated UFO reports at various times.
Among the best known government studies are the ghost rockets investigation by the Swedish military (1946–1947), Project Blue Book, previously Project Sign and Project Grudge, conducted by the United States Air Force from 1947 until 1969, the secret U.S. Army/Air Force Project Twinkle investigation into green fireballs (1948–1951), the secret USAF Project Blue Book Special Report #14 by the Battelle Memorial Institute, and Brazilian Air Force Operation Saucer (1977). France has had an ongoing investigation (GEPAN/SEPRA/GEIPAN) within its space agency CNES since 1977; the government of Uruguay has had a similar investigation since 1989.
Project SignProject Sign in 1948 produced a highly classified finding (see Estimate of the Situation) that the best UFO reports probably had an extraterrestrial explanation; the private but high-level French COMETA study of 1999 reached a similar conclusion. A top secret Swedish military opinion given to the USAF in 1948 stated that some of their analysts believed that the 1946 ghost rockets and later flying saucers had extraterrestrial origins. (see Ghost rockets for document). In 1954 German rocket scientist Hermann Oberth revealed that an internal West German government investigation, which he headed, had arrived at an extraterrestrial conclusion, but this study was never made public.
Project MagnetClassified, internal reports by the Canadian Project Magnet in 1952 and 1953 also assigned high probability to extraterrestrial origins. Publicly, however, neither Project Magnet nor later Canadian defense studies ever stated such a conclusion.
Project GrudgeProject Sign was dismantled and became Project Grudge at the end of 1948. Angered by the low quality of investigations by Grudge, the Air Force Director of Intelligence reorganized it as Project Blue Book in late 1951, placing Ruppelt in charge. Blue Book closed down in 1970, using the Condon Commission's negative conclusion as a rationale, thus ending official Air Force UFO investigations. However, a 1969 USAF document, known as the Bolender memo, along with later government documents, revealed that non-public U.S. government UFO investigations continued after 1970. The Bollender memo first stated that "reports of unidentified flying objects that could affect national security . . . are not part of the Blue Book system," indicating that more serious UFO incidents already were handled outside the public Blue Book investigation. The memo then added, "reports of UFOs which could affect national security would continue to be handled through the standard Air Force procedures designed for this purpose." In addition, in the late 1960s a chapter on UFOs in the Space Sciences course at the U.S. Air Force Academy gave serious consideration to possible extraterrestrial origins. When word of the curriculum became public, the Air Force in 1970 issued a statement to the effect that the book was outdated and that cadets instead were being informed of the Condon report's negative conclusion.
USAF Regulation 200-2Air Force Regulation 200-2, issued in 1953 and 1954, defined an Unidentified Flying Object ("UFOB") as "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." The regulation also said UFOBs were to be investigated as a "possible threat to the security of the United States" and "to determine technical aspects involved." The regulation went on to say that "it is permissible to inform news media representatives on UFOB's when the object is positively identified as a familiar object," but added: "For those objects which are not explainable, only the fact that ATIC [Air Technical Intelligence Center] will analyze the data is worthy of release, due to many unknowns involved."
Project BluebookJ. Allen Hynek, a trained astronomer who served as a scientific advisor for Project Bluebook, was initially skeptical of UFO reports, but eventually came to the conclusion that many of them could not be satisfactorily explained and was highly critical of what he described as "the cavalier disregard by Project Blue Book of the principles of scientific investigation."  Leaving government work, he founded the privately funded Center for UFO Studies, to whose work he devoted the rest of his life. Other private groups studying the phenomenon include the Mutual UFO Network, a grass roots organization whose investigator's handbooks go into great detail on the documentation of alleged UFO sightings.
Like Hynek, Jacques Vallée, a scientist and prominent UFO researcher, has pointed to what he believes is the scientific deficiency of most UFO research, including government studies. He complains of the mythology and cultism often associated with the phenomenon, but alleges that several hundred professional scientists—a group both he and Hyneck have termed "the invisible college"—continue to study UFOs in private.
Scientific studiesThe study of UFOs has received little support in mainstream scientific literature. Official studies ended in the U.S. in December 1969, following the statement by the government scientist Edward Condon that further study of UFOs could not be justified on grounds of scientific advancement. The Condon report and its conclusions were endorsed by the National Academy of Scientists, of which Condon was a member. On the other hand, a scientific review by the UFO subcommittee of the AIAA disagreed with Condon's conclusion, noting that at least 30 percent of the cases studied remained unexplained and that scientific benefit might be gained by continued study.
Critics argue that all UFO evidence is anecdotal and can be explained as prosaic natural phenomena. Defenders of UFO research counter that knowledge of observational data, other than what is reported in the popular media, is limited in the scientific community and that further study is needed.
No official government investigation has ever publicly concluded that UFOs are indisputably real, physical objects, extraterrestrial in origin, or of concern to national defense. These same negative conclusions also have been found in studies that were highly classified for many years, such as the UK's Flying Saucer Working Party, Project Condign, the US CIA-sponsored Robertson Panel, the US military investigation into the green fireballs from 1948 to 1951, and the Battelle Memorial Institute study for the USAF from 1952 to 1955 (Project Blue Book Special Report #14).
Some public government reports have acknowledged the possibility of physical reality of UFOs, but have stopped short of proposing extraterrestrial origins, though not dismissing the possibility entirely. Examples are the Belgian military investigation into large triangles over their airspace in 1989–1991 and the recent 2009 Uruguay Air Force study conclusion (see below).
Some private studies have been neutral in their conclusions, but argued that the inexplicable core cases call for continued scientific study. Examples are the Sturrock Panel study of 1998 and the 1970 AIAA review of the Condon Report.
United StatesUS investigations into UFOs include:
- The Interplanetary Phenomenon Unit (IPU), established by the US Army sometime in the 1940s, and about which little is known. In 1987 British UFO researcher Timothy Good received from the Army's director of couunter-intelligence a letter confirming the existence of the IPU. The letter stated that "the aforementioned Army unit was disestablished during the late 1950s and never reactivated. All records pertaining to this unit were surrendered to the U.S. Air Force Office of Special Investigations in conjunction with operation BLUEBOOK." The IPU records have never been released.
- Project Blue Book, previously Project Sign and Project Grudge, conducted by the United States Air Force from 1947 until 1969
- The secret U.S. Army/Air Force Project Twinkle investigation into green fireballs (1948–1951)
- Ghost rockets investigations by the Swedish, U.K., U.S., and Greek militaries (1946–1947)
- The secret CIA Office of Scientific Investigation (OS/I) study (1952–53)
- The secret CIA Robertson Panel (1953)
- The secret USAF Project Blue Book Special Report No. 14 by the Battelle Memorial Institute (1951–1954)
- The Brookings Report (1960), commissioned by NASA
- The public Condon Committee (1966–1968)
- The private, internal RAND Corporation study (1968)
- The private Sturrock Panel (1998)
The investigation of UFOs has also attracted many civilians, who in the U.S formed research groups such as National Investigations Committee On Aerial Phenomena (NICAP, active 1956–1980), Aerial Phenomena Research Organization (APRO, 1952–1988), Mutual UFO Network (MUFON, 1969–), and Center for UFO Studies (CUFOS, 1973–).
In November 2011, the White House released an official response to two petitions asking the U.S. government to acknowledge formally that aliens have visited this planet and to disclose any intentional withholding of government interactions with extraterrestrial beings. According to the response, "The U.S. government has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race." Also, according to the response, there is "no credible information to suggest that any evidence is being hidden from the public's eye." The response further noted that efforts, like SETI, the Kepler space telescope and the NASA Mars rover, continue looking for signs of life. The response noted "odds are pretty high" that there may be life on other planets but "the odds of us making contact with any of them—especially any intelligent ones—are extremely small, given the distances involved."
Post-1947 sightingsFollowing the large U.S. surge in sightings in June and early July 1947, on July 9, 1947, Army Air Force (AAF) intelligence, in cooperation with the FBI, began a formal investigation into selected sightings with characteristics that could not be immediately rationalized, which included Kenneth Arnold’s and that of the United Airlines crew. The AAF used "all of its top scientists" to determine whether "such a phenomenon could, in fact, occur." The research was "being conducted with the thought that the flying objects might be a celestial phenomenon," or that "they might be a foreign body mechanically devised and controlled." Three weeks later in a preliminary defense estimate, the air force investigation decided that, "This ‘flying saucer’ situation is not all imaginary or seeing too much in some natural phenomenon. Something is really flying around."
A further review by the intelligence and technical divisions of the Air Materiel Command at Wright Field reached the same conclusion. It reported that "the phenomenon is something real and not visionary or fictitious," that there were objects in the shape of a disc, metallic in appearance, and as big as man-made aircraft. They were characterized by "extreme rates of climb [and] maneuverability," general lack of noise, absence of trail, occasional formation flying, and "evasive" behavior "when sighted or contacted by friendly aircraft and radar," suggesting a controlled craft. It was therefore recommended in late September 1947 that an official Air Force investigation be set up to investigate the phenomenon. It was also recommended that other government agencies should assist in the investigation.
Project SignThis led to the creation of the Air Force’s Project Sign at the end of 1947, one of the earliest government studies to come to a secret extraterrestrial conclusion. In August 1948 Sign investigators wrote a top-secret intelligence estimate to that effect, but the Air Force Chief of Staff Hoyt Vandenberg ordered it destroyed. The existence of this suppressed report was revealed by several insiders who had read it, such as astronomer and USAF consultant J. Allen Hynek and Capt. Edward J. Ruppelt, the first head of the USAF's Project Blue Book.
Another highly classified U.S. study was conducted by the CIA's Office of Scientific Investigation (OS/I) in the latter half of 1952 in response to orders from the National Security Council (NSC). This study concluded UFOs were real physical objects of potential threat to national security. One OS/I memo to the CIA Director (DCI) in December read, "...the reports of incidents convince us that there is something going on that must have immediate attention.... Sightings of unexplained objects at great altitudes and traveling at high speeds in the vicinity of major U.S. defense installations are of such a nature that they are not attributable to natural phenomena or any known types of aerial vehicles." The matter was considered so urgent that OS/I drafted a memorandum from the DCI to the NSC proposing that the NSC establish an investigation of UFOs as a priority project throughout the intelligence and the defense research and development community. It also urged the DCI to establish an external research project of top-level scientists, now known as the Robertson Panel to analyze the problem of UFOs. The OS/I investigation was called off after the Robertson Panel's negative conclusions in January 1953.
The Condon CommitteeA public research effort conducted by the Condon Committee for the USAF, which arrived at a negative conclusion in 1968, marked the end of the US government's official investigation of UFOs, though various government intelligence agencies continue unofficially to investigate or monitor the situation.
Controversy has surrounded the Condon report, both before and after it was released. It has been observed that the report was "harshly criticized by numerous scientists, particularly at the powerful AIAA ... [which] recommended moderate, but continuous scientific work on UFOs". In an address to the AAAS, James E. McDonald stated that he believed science had failed to mount adequate studies of the problem and criticized the Condon report and earlier studies by the US Air Force as scientifically deficient. He also questioned the basis for Condon's conclusions and argued that the reports of UFOs have been "laughed out of scientific court." J. Allen Hynek, an astronomer who worked as a USAF consultant from 1948, sharply criticized Condon Committee Report and later wrote two nontechnical books that set forth the case for continuing to investigate UFO reports.
Ruppelt recounted his experiences with Project Blue Book, a USAF investigation that preceded Condon's.
- The Roswell Incident (1947) involved New Mexico residents, local law enforcement officers, and the US military, the latter of whom allegedly collected physical evidence from the UFO crash site.
- The Mantell UFO Incident January 7, 1948
- The Betty and Barney Hill abduction (1961) was the first reported abduction incident.
- In the Kecksburg Incident, Pennsylvania (1965), residents reported seeing a bell shaped object crash in the area. Police officers, and possibly military personnel, were sent to investigate.
- The Travis Walton abduction case (1975): The movie Fire in the Sky was based on this event, but embellished greatly the original account.
- The "Phoenix Lights" March 13, 1997
CanadaIn Canada, the Department of National Defence has dealt with reports, sightings and investigations of UFOs across Canada. In addition to conducting investigations into crop circles in Duhamel, Alberta, it still considers "unsolved" the Falcon Lake incident in Manitoba and the Shag Harbour incident in Nova Scotia.
Early Canadian studies included Project Magnet (1950–1954) and Project Second Storey (1952–1954), supported by the Defence Research Board. These studies were headed by Canadian Department of Transport radio engineer Wilbert B. Smith, who later publicly supported extraterrestrial origins.
In the Shag Harbour incident, a large object sequentially flashing lights was seen and heard to dive into the water by multiple witnesses. The Royal Canadian Mounted Police and many local residents also witnessed a light floating on the water immediately afterward, and a large patch of unusual yellow foam when a water search was initiated. Multiple government agencies were eventually involved in trying to identify the crashed object and searching for it. Canadian naval divers later purportedly found no wreckage. In official documents, the object was called a "UFO" because no conventional explanation for the crashed object was discovered. Around the same time, both the Canadian and US military were involved in another UFO-related search at Shelburne, Nova Scotia, approximately 30 miles from Shag Harbour.
FranceOn March 2007, the French Centre National d'Études Spatiales (CNES) published an archive of UFO sightings and other phenomena online.
French studies include GEPAN/SEPRA/GEIPAN (1977–), within the French space agency CNES, the longest ongoing government-sponsored investigation. About 14% of some 6000 cases studied remained unexplained. The official opinion of GEPAN/SEPRA/GEIPAN has been neutral or negative, but the three heads of the studies have gone on record in stating that UFOs were real physical flying machines beyond our knowledge or that the best explanation for the most inexplicable cases was an extraterrestrial one.
The French COMETA panel (1996–1999) was a private study undertaken mostly by aerospace scientists and engineers affiliated with CNES and high-level French Air Force military intelligence analysts, with ultimate distribution of their study intended for high government officials. The COMETA panel likewise concluded the best explanation for the inexplicable cases was the extraterrestrial hypothesis and went further in accusing the United States government of a massive cover-up.
United KingdomThe UK's Flying Saucer Working Party published its final report in 1951, which remained secret for over 50 years. The Working Party concluded that all UFO sightings could be explained as misidentifications of ordinary objects or phenomena, optical illusions, psychological misperceptions/aberrations, or hoaxes. The report stated: "We accordingly recommend very strongly that no further investigation of reported mysterious aerial phenomena be undertaken, unless and until some material evidence becomes available."
Eight file collections on UFO sightings, dating from 1978 to 1987, were first released on May 14, 2008, to the UK National Archives by the Ministry of Defence. Although kept secret from the public for many years, most of the files have low levels of classification and none are classified Top Secret. 200 files are set to be made public by 2012. The files are correspondence from the public sent to government officials, such as the MoD and Margaret Thatcher. The MoD released the files under the Freedom of Information Act due to requests from researchers. These files include, but are not limited to, UFOs over Liverpool and the Waterloo Bridge in London.
On October 20, 2008 more UFO files were released. One case released detailed that in 1991 an Alitalia passenger aircraft was approaching Heathrow Airport when the pilots saw what they described as a "cruise missile" fly extremely close to the cockpit. The pilots believed that a collision was imminent. UFO expert David Clarke says that this is one of the most convincing cases for a UFO he has come across.
A secret study of UFOs was undertaken for the UK’s Ministry of Defence (MoD) between 1996 and 2000 and was code-named Project Condign. The resulting report, titled "Unidentified Aerial Phenomena in the UK Defence Region", was publicly released in 2006, but the identity and credentials of whomever constituted Project Condign remains classified. The report confirmed earlier findings that the main causes of UFO sightings are misidentification of man-made and natural objects. The report noted: "No artefacts of unknown or unexplained origin have been reported or handed to the UK authorities, despite thousands of UAP reports. There are no SIGINT, ELINT or radiation measurements and little useful video or still IMINT." It concluded: "There is no evidence that any UAP, seen in the UKADR [UK Air Defence Region], are incursions by air-objects of any intelligent (extraterrestrial or foreign) origin, or that they represent any hostile intent." A little-discussed conclusion of the report was that novel meteorological plasma phenomenon akin to Ball Lightning are responsible for "the majority, if not all" of otherwise inexplicable sightings, especially reports of Black Triangle UFOs.
In August 2009 The Black Vault internet archive announced the release by the British government of more than 4,000 pages of declassified records. The records include information on the Rendlesham Forest incident, crop circles, a UFO attack on a cemetery and even reports of alien abduction claims.
On December 1, 2009, the British Ministry of Defense (MoD) quietly closed down its UFO investigations unit. The unit's hotline and email address were suspended by the Ministry of Defense on that date. The MoD said there was no value in continuing to receive and investigate sightings in a release, stating
- "... in over fifty years, no UFO report has revealed any evidence of a potential threat to the United Kingdom. The MoD has no specific capability for identifying the nature of such sightings. There is no Defence benefit in such investigation and it would be an inappropriate use of defence resources. Furthermore, responding to reported UFO sightings diverts MoD resources from tasks that are relevant to Defence."
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- According to records released on August 5, 2010, British wartime prime minister Winston Churchill banned the reporting for 50 years of an alleged UFO incident because of fears it could create mass panic. Reports given to Churchill asserted that the incident involved an RAF reconnaissance plane returning from a mission in France or Germany toward the end of the Second World War. It was over or near the English coastline when it was allegedly intercepted by a strange metallic object that matched the aircraft's course and speed for a time before accelerating away and disappearing. The plane's crew were reported to have photographed the object, which they said had "hovered noiselessly" near the aircraft, before moving off. According to the documents, details of the coverup emerged when a man wrote the government in 1999 seeking to find out more about the incident and described how his grandfather, who had served with the Royal Air Force (RAF) in the Second World War, was present when Churchill and U.S. General Dwight Eisenhower discussed how to deal with the UFO encounter. The files come from more than 5,000 pages of UFO reports, letters and drawings from members of the public, as well as questions raised in Parliament. They are available to download from The National Archives website.
- In the April 1957 West Freugh Incident in Scotland, named after the principal military base involved, two unidentified objects flying high over the UK were tracked by radar operators. The objects were reported to operate at speeds and perform maneuvers beyond the capability of any known craft. Also significant is their alleged size, which – based on the radar returns – was closer to that of a ship than an aircraft.
- In the Rendlesham Forest incident of December 1980, US military personnel witnessed UFOs near the air base at Woodbridge, Suffolk, over a period of three nights. On one night the deputy base commander, Col. Charles Halt, and other personnel followed one or more UFOs that were moving in and above the forest for several hours. Col. Halt made an audio recording while this was happening and subsequently wrote an official memorandum summarizing the incident. After retirement from the military, he said that he had deliberately downplayed the event (officially termed 'Unexplained Lights') to avoid damaging his career. Other base personnel are said to have observed one of the UFOs, which had landed in the forest, and even gone up to and touched it.
UruguayThe Uruguayan Air Force has been conducting an ongoing UFO investigation since 1989 and analyzed 2100 cases, of which they regard only 40 (about 2%) as definitely lacking any conventional explanation. All files have recently been declassified. The unexplained cases include military jet interceptions, abductions, cattle mutilations, and physical landing trace evidence. Colonel Ariel Sanchez, who currently heads the investigation, summarized its findings as follows: "The commission managed to determine modifications to the chemical composition of the soil where landings are reported. The phenomenon exists. It could be a phenomenon that occurs in the lower sectors of the atmosphere, the landing of aircraft from a foreign air force, up to the extraterrestrial hypothesis. It could be a monitoring probe from outer space, much in the same way that we send probes to explore distant worlds. The UFO phenomenon exists in the country. I must stress that the Air Force does not dismiss an extraterrestrial hypothesis based on our scientific analysis."
Astronomer reportsThe United States Air Force's Project Blue Book files indicate that approximately 1 % of all unknown reports came from amateur and professional astronomers or other users of telescopes (such as missile trackers or surveyors). In 1952, astronomer J. Allen Hynek, then a consultant to Blue Book, conducted a small survey of 45 fellow professional astronomers. Five reported UFO sightings (about 11%). In the 1970s, astrophysicist Peter A. Sturrock conducted two large surveys of the American Institute of Aeronautics and Astronautics and American Astronomical Society. About 5 % of the members polled indicated that they had had UFO sightings.
Astronomer Clyde Tombaugh, who admitted to six UFO sightings, including three green fireballs, supported the Extraterrestrial hypothesis (ETH) for UFOs and stated he thought scientists who dismissed it without study were being "unscientific". Another astronomer was Lincoln LaPaz, who had headed the Air Force's investigation into the green fireballs and other UFO phenomena in New Mexico. LaPaz reported two personal sightings, one of a green fireball, the other of an anomalous disc-like object. (Both Tombaugh and LaPaz were part of Hynek's 1952 survey.) Hynek himself took two photos through the window of a commercial airliner of a disc-like object that seemed to pace his aircraft. Even later UFO debunker Donald Menzel filed a UFO report in 1949.
In 1980, a survey of 1800 members of various amateur astronomer associations by Gert Helb and Hynek for the Center for UFO Studies (CUFOS) found that 24 % responded "yes" to the question "Have you ever observed an object which resisted your most exhaustive efforts at identification?"
Identification of UFOsIdentification studies of UFOs). The most commonly found identified sources of UFO reports are:
- Astronomical objects (bright stars, planets, meteors, re-entering man-made spacecraft, artificial satellites, and the moon)
- Aircraft (Aerial advertising and other aircraft, missile launches)
- Balloons (weather balloons, prank balloons, large research balloons)
- Other atmospheric objects and phenomena (birds, unusual clouds, kites, flares)
- Light phenomena (mirages, Fata Morgana, moon dogs, searchlights and other ground lights, etc.)
The official French government UFO investigation (GEPAN/SEPRA/GEIPAN), run within the French space agency CNES between 1977 and 2004, scientifically investigated about 6000 cases and found that 13.5 % defied any rational explanation, 46 % were deemed definitely or likely identifiable, while 41 % lacked sufficient information for classification.
An individual 1979 study by CUFOS researcher Allan Hendry found, as did other investigations, that only a small percentage of cases he investigated were hoaxes (<1 actually="actually" and="and" attributed="attributed" class="reference" hendry="hendry" honest="honest" id="cite_ref-72" inexperience="inexperience" misidentifications="misidentifications" misperception.="misperception." most="most" of="of" or="or" phenomena.="phenomena." prosaic="prosaic" sightings="sightings" sup="sup" that="that" these="these" to="to" were="were">1>
Extraterrestrial hypothesisWhile technically a UFO refers to any unidentified flying object, in modern popular culture the term UFO has generally become synonymous with alien spacecraft; however, the term ETV (ExtraTerrestrial Vehicle) is sometimes used to separate this explanation of UFOs from totally earthbound explanations.
Proponents argue that because these objects appear to be technological and not natural phenomena and are alleged to display flight characteristics or have shapes seemingly unknown to conventional technology, the conclusion is that they must not be from Earth. Though UFO sightings have occurred throughout recorded history, modern interest in them dates from World War II (see foo fighter), further fueled in the late 1940s by Kenneth Arnold's report of a close encounter, which led to coining of the term flying saucer, and the Roswell UFO Incident. Since then governments have investigated UFO reports, often from a military perspective, and UFO researchers have investigated, written about, and created organizations devoted to the subject. One such investigation, the UK's Project Condign, made public in 2006, attributed unaccountable UFO sightings to a hitherto unknown and scientifically unexplained "plasma field." It also concluded that Russian, former Soviet Republics, and Chinese authorities had made a co-ordinated effort to understand the UFO phenomenon and that military organizations, particularly in Russia, had done "considerably more work (than is evident from open sources)" on military applications stemming from their UFO research. The report also noted that "several aircraft have been destroyed and at least four pilots have been killed 'chasing UFOs'."
Associated claimsBesides anecdotal visual sightings, reports sometimes include claims of other kinds of evidence, including cases studied by the military and various government agencies of different countries (such as Project Blue Book, the Condon Committee, the French GEPAN/SEPRA, and Uruguay's current Air Force study).
A comprehensive scientific review of cases where physical evidence was available was carried out by the 1998 Sturrock UFO panel, with specific examples of many of the categories listed below.
- Radar contact and tracking, sometimes from multiple sites. These have included military personnel and control tower operators, simultaneous visual sightings, and aircraft intercepts. One such recent example were the mass sightings of large, silent, low-flying black triangles in 1989 and 1990 over Belgium, tracked by NATO radar and jet interceptors, and investigated by Belgium's military (included photographic evidence). Another famous case from 1986 was the JAL 1628 case over Alaska investigated by the FAA.
- Photographic evidence, including still photos, movie film, and video.
- Claims of physical trace of landing UFOs, including ground impressions, burned and/or desiccated soil, burned and broken foliage, magnetic anomalies[specify], increased radiation levels, and metallic traces. See, e. g. Height 611 UFO Incident or the 1964 Lonnie Zamora's Socorro, New Mexico encounter of the USAF Project Blue Book cases). A well-known example from December 1980 was the USAF Rendlesham Forest Incident in England. Another occurred in January 1981 in Trans-en-Provence and was investigated by GEPAN, then France's official government UFO-investigation agency. Project Blue Book head Edward J. Ruppelt described a classic 1952 CE2 case involving a patch of charred grass roots.
- Physiological effects on people and animals including temporary paralysis, skin burns and rashes, corneal burns, and symptoms superficially resembling radiation poisoning, such as the Cash-Landrum incident in 1980.
- Animal/cattle mutilation cases, that some feel are also part of the UFO phenomenon.
- Biological effects on plants such as increased or decreased growth, germination effects on seeds, and blown-out stem nodes (usually associated with physical trace cases or crop circles)
- Electromagnetic interference (EM) effects. A famous 1976 military case over Tehran, recorded in CIA and DIA classified documents, was associated with communication losses in multiple aircraft and weapons system failure in an F-4 Phantom II jet interceptor as it was about to fire a missile on one of the UFOs.
- Apparent remote radiation detection, some noted in FBI and CIA documents occurring over government nuclear installations at Los Alamos National Laboratory and Oak Ridge National Laboratory in 1950, also reported by Project Blue Book director Ed Ruppelt in his book.
- Claimed artifacts of UFOs themselves, such as 1957, Ubatuba, Brazil, magnesium fragments analyzed by the Brazilian government and in the Condon Report and by others. The 1964 Socorro/Lonnie Zamora incident also left metal traces, analyzed by NASA. A more recent example involves "the Bob White object" a tear drop shaped object recovered by Bob White and was featured in the TV show UFO Hunters.
- Angel hair and angel grass, possibly explained in some cases as nests from ballooning spiders or chaff.
Reverse engineeringAttempts have been made to reverse engineer the possible physics behind UFOs through analysis of both eyewitness reports and the physical evidence, on the assumption that they are powered vehicles. Examples are former NASA and nuclear engineer James McCampbell in his book Ufology, NACA/NASA engineer Paul R. Hill in his book Unconventional Flying Objects, and German rocketry pioneer Hermann Oberth. Among subjects tackled by McCampbell, Hill, and Oberth was the question of how UFOs can fly at supersonic speeds without creating a sonic boom. McCampbell's proposed solution is microwave plasma parting the air in front of the craft. In contrast, Hill and Oberth believed UFOs utilize an as-yet-unknown anti-gravity field to accomplish the same thing as well as provide propulsion and protection of occupants from the effects of high acceleration.
UfologyUfology is a neologism describing the collective efforts of those who study UFO reports and associated evidence.
|This section does not cite any references or sources. (March 2009)|
- Saucer, toy-top, or disk-shaped "craft" without visible or audible propulsion. (day and night)
- Large triangular "craft" or triangular light pattern, usually reported at night.
- Cigar-shaped "craft" with lighted windows (Meteor fireballs are sometimes reported this way, but are very different phenomena).
- Other: chevrons, (equilateral) triangles, crescent, boomerangs, spheres (usually reported to be shining, glowing at night), domes, diamonds, shapeless black masses, eggs, pyramids and cylinders, classic "lights".
Hynek's system involves dividing the sighted object by appearance, subdivided further into the type of "close encounter" (a term from which the film director Steven Spielberg derived the title of his 1977 UFO movie, Close Encounters of the Third Kind).
Jacques Vallée's system classifies UFOs into five broad types, each with from three to five subtypes that vary according to type.
Scientific skepticismA scientifically skeptical group that has for many years offered critical analysis of UFO claims is the Committee for Skeptical Inquiry (CSI).
Responding to local beliefs that "extraterrestrial beings" in UFOs were responsible for crop circles appearing in Indonesia, the government and the National Aeronautics and Space Agency (Lapan) described them as "man-made". Thomas Djamaluddin, research professor of astronomy and astrophysics at Lapan stated: "We have come to agree that this 'thing' cannot be scientifically proven. A professor at the Indonesian National Aeronautics and Space Agency put UFOs in the category of pseudoscience."
Conspiracy theoriesUFOs are sometimes an element of conspiracy theories in which governments are allegedly intentionally "covering up" the existence of aliens or sometimes collaborating with them. There are many versions of this story; some are exclusive, while others overlap with various other conspiracy theories.
In the U.S., an opinion poll conducted in 1997 suggested that 80 % of Americans believed the U.S. government was withholding such information. Various notables have also expressed such views. Some examples are astronauts Gordon Cooper and Edgar Mitchell, Senator Barry Goldwater, Vice Admiral Roscoe H. Hillenkoetter (the first CIA director), Lord Hill-Norton (former British Chief of Defense Staff and NATO head), the 1999 high-level French COMETA report by various French generals and aerospace experts, and Yves Sillard (former director of the French space agency CNES, new director of French UFO research organization GEIPAN).
It has also been suggested by a few paranormal authors that all or most human technology and culture is based on extraterrestrial contact. See also ancient astronauts.
Allegations of evidence suppressionThere have been allegations of suppression of UFO related evidence for many decades. There are claims that physical evidence might have been removed and/or destroyed/suppressed by some governments.
- The Maury Island incident
- The Ummo affair, a decades-long series of detailed letters and documents allegedly from extraterrestrials. The total length of the documents is at least 1000 pages, and some estimate that further undiscovered documents may total nearly 4000 pages. A José Luis Jordan Pena came forward in the early nineties claiming responsibility for the phenomenon, and most[who?] consider there to be little reason to challenge his claims.
- George Adamski over the space of two decades made various claims about his meetings with telepathic aliens from nearby planets. He claimed that photographs of the far side of the moon taken by a Soviet orbital probe in 1959 were fake, and that there were cities, trees and snow-capped mountains on the far side of the moon. Among copycats was a shadowy British figure named Cedric Allingham.
- Ed Walters, a building contractor, in 1987 allegedly perpetrated a hoax in Gulf Breeze, Florida. Walters claimed at first having seen a small UFO flying near his home and took some photographs of the craft. Walters reported and documented a series of UFO sightings over a period of three weeks and took several photographs. These sightings became famous and were called Gulf Breeze UFO incident. Three years later, in 1990, after the Walters family had moved, the new residents discovered a model of a UFO poorly hidden in the attic that bore an undeniable resemblance to the craft in Walters' photographs. Most investigators like the forensic photo expert William G. Hyzer now consider the sightings to be a hoax.
- Warren William "Billy" Smith is a popular writer and confessed hoaxster.
In popular cultureUFOs constitute a widespread international cultural phenomenon of the last 60 years. Gallup polls rank UFOs near the top of lists for subjects of widespread recognition. In 1973, a survey found that 95 percent of the public reported having heard of UFOs, whereas only 92 percent had heard of U.S. President Gerald Ford in a 1977 poll taken just nine months after he left the White House. A 1996 Gallup poll reported that 71 percent of the United States population believed that the government was covering up information regarding UFOs. A 2002 Roper poll for the Sci Fi Channel found similar results, but with more people believing that UFOs are extraterrestrial craft. In that latest poll, 56 percent thought UFOs were real craft and 48 percent that aliens had visited the Earth. Again, about 70 percent felt the government was not sharing everything it knew about UFOs or extraterrestrial life. In the film Yellow Submarine, Ringo states that the yellow submarine that is following him "must be one of them unidentified flying cupcakes."  Another effect of the flying saucer type of UFO sightings has been Earth-made flying saucer craft in space fiction, for example the Earth spacecraft Starship C-57D in Forbidden Planet, the Jupiter Two in Lost in Space, and the saucer section of the USS Enterprise in Star Trek, and many others.
- List of UFO sightings
- List of alleged aircraft-UFO incidents and near misses
- Extraterrestrial hypothesis (ETH)
- Extraterrestrial life
- Project Blue Book
- Roswell incident
- Declassification of UFO documents
|This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (January 2010)|
- Thomas E. Bullard, "UFOs: Lost in the Myths", pages 141–191 in "UFOs, the Military, and the Early Cold War Era", pages 82–121 in "UFOs and Abductions: Challenging the Borders of Knowledge" David M. Jacobs, editor; 2000, University Press of Kansas, ISBN 0-7006-1032-4
- Jerome Clark, The UFO Book: Encyclopedia of the Extraterrestrial, 1998, Visible Ink Press, ISBN 1-57859-029-9. Many classic cases and UFO history provided in great detail; highly documented.
- J. Deardorff, B. Haisch, B. Maccabee, Harold E. Puthoff (2005). "Inflation-Theory Implications for Extraterrestrial Visitation". Journal of the British Interplanetary Society 58: 43–50. http://www.ufoskeptic.org/JBIS.pdf.
- Curran, Douglas. In Advance of the Landing: Folk Concepts of Outer Space. (revised edition), Abbeville Press, 2001. ISBN 0-7892-0708-7. Non-sensational but fair treatment of contemporary UFO legend and lore in N. America, including the so-called "contactee cults." The author traveled the United States with his camera and tape recorder and directly interviewed many individuals.
- Hall, Richard H., editor. The UFO Evidence: Volume 1. 1964, NICAP, reissued 1997, Barnes & Noble Books, ISBN 0-7607-0627-1. Well-organized, exhaustive summary and analysis of 746 unexplained NICAP cases out of 5000 total cases—a classic.
- Hall, Richard H. The UFO Evidence: A Thirty-Year Report. Scarecrow Press, 2001. ISBN 0-8108-3881-8. Another exhaustive case study, more recent UFO reports.
- Hendry, Alan. The UFO Handbook: A Guide to Investigating, Evaluating, and Reporting UFO Sightings. New York: Doubleday & Co., 1979. ISBN 0-385-14348-6. Skeptical but balanced analysis of 1300 CUFOS UFO cases.
- Hynek, J. Allen. The UFO Experience: A scientific inquiry. Henry Regnery Co., 1972.
- Hynek, J. Allen. The Hynek UFO Report. New York: Barnes & Noble Books, 1997. ISBN 0-7607-0429-5. Analysis of 640 high-quality cases through 1969 by UFO legend Hynek.
- Rose, Bill and Buttler, Tony. Flying Saucer Aircraft (Secret Projects). Leicester, UK: Midland Publishing, 2006. ISBN 1-85780-233-0.
- Sagan, Carl & Page. Thornton, editors. UFOs: A Scientific Debate. \Cornell University Press, 1996. ISBN 0-7607-0192-2.
- Sheaffer, Robert The UFO Verdict: Examining the Evidence, 1986, Prometheus Books ISBN 0-87975-338-2
- Sheaffer, Robert UFO Sightings: The Evidence, 1998, Prometheus Books, ISBN 1-57392-213-7 (revised edition of The UFO Verdict)
- Sturrock, Peter A. (1999). The UFO Enigma: A New Review of the Physical Evidence. New York: Warner Books. ISBN 0-446-52565-0
- Canada's Unidentified Flying Objects: The Search for the Unknown, a virtual museum exhibition at Library and Archives Canada
- Philip Plait (2002). Bad Astronomy: Misconceptions and Misuses Revealed, from Astrology to the Moon Landing "Hoax". John Wiley & Sons, ISBN 0-471-40976-6. (Chapter 20: Misidentified Flying Objects: UFOs and Illusions of the Mind and Eye.)
- Ian Ridpath "Astronomical Causes of UFOs"
- Michael A. Seeds. (1995). Horizons: Exploring the Universe, Wadsworth Publishing, ISBN 0-534-24889-6 and ISBN 0-534-24890-X. (Appendix A)
- Robert Sheaffer (2011). Psychic Vibrations: Skeptical Giggles from the Skeptical Inquirer, Create Space, ISBN 1-4636-0157-3.
- Carl G. Jung, "Flying Saucers: A Modern Myth of Things Seen in the Skies" (translated by R.F.C. Hull); 1979, Princeton University Press, ISBN 0-691-01822-7
- Armando Simon,A Nonreactive, Quantitative Study of Mass Behavior with Emphasis on the Cinema as Behavior Catalyst," Psychological Reports, 1981, 48, 775–785.
- Richard Haines"UFO Phenomena and the Behavioral Scientist." Metuchen: Scarecrow Press, 1979.
- Armando Simon "UFOs: Testing for the Existence of Air Force Censorship." Psychology, 1976, 13, 3–5.
- Armando Simon "Psychology and the UFOs." The Skeptical Inquirer. 1984, 8, 355–367.
- Dr David Clarke, The UFO Files. The Inside Story of Real-life Sightings, 2009, The National Archives, Kew. ISBN 978-1-905615-50-6. Reports from the UK government files
- Richard M. Dolan, UFOs and the National Security State: An Unclassified History, Volume One: 1941–1973, 2000, Keyhole Publishing, ISBN 0-9666885-0-3. Dolan is a professional historian.
- Downes, Jonathan Rising of the Moon. 2nd ed. Bangor: Xiphos, 2005.
- Lawrence Fawcett & Barry J. Greenwood, The UFO Cover-Up (Originally Clear Intent), 1992, Fireside Books (Simon & Schuster), ISBN 0-671-76555-8. Many UFO documents.
- Timothy Good, Above Top Secret, 1988, William Morrow & Co., ISBN 0-688-09202-0. Many UFO documents.
- Timothy Good, Need to Know: UFOs, the Military, and Intelligence, 2007, Pegasus Books, ISBN 978-1-933648-38-5. Update of Above Top Secret with new cases and documents
- Bruce Maccabee, UFO FBI Connection, 2000, Llewellyn Publications, ISBN 1-56718-493-6
- Kevin Randle, Project Blue Book Exposed, 1997, Marlowe & Company, ISBN 1-56924-746-3
- Edward J. Ruppelt, The Report On Unidentified Flying Objects, 1956, Doubleday & Co. online. A UFO classic by insider Ruppelt, the first head of the USAF Project Blue Book
- LeRoy F. Pea, Government Involvement in the UFO Coverup, or earlier title History of UFO Crash/Retrievals", 1988, PEA RESEARCH.
- Paul R. Hill, Unconventional Flying Objects: a scientific analysis, 1995, Hampton Roads Publishing Co., ISBN 1-57174-027-9. Analysis of UFO technology by pioneering NACA/NASA aerospace engineer.
- James M. McCampbell, Ufology: A Major Breakthrough in the Scientific Understanding of Unidentified Flying Objects, 1973, 1976, Celestial Arts, ISBN 0-89087-144-2 full-text online. Another analysis by former NASA and nuclear engineer.
- James M. McCampbell, Physical effects of UFOs upon people, 1986, paper.
- Antonio F. Rullán, Odors from UFOs: Deducing Odorant Chemistry and Causation from Available Data, 2000, preliminary paper.
- Jack Sarfatti, "Super Cosmos", 2005 (Authorhouse)
- S. Krasnikov (2003). "The quantum inequalities do not forbid spacetime shortcuts". Physical Review D 67 (10): 104013. arXiv:gr-qc/0207057. Bibcode 2003PhRvD..67j4013K. doi:10.1103/PhysRevD.67.104013.
- L. H. Ford and T. A. Roman (1996). "Quantum field theory constrains traversable wormhole geometries". Physical Review D 53 (10): 5496. arXiv:gr-qc/9510071. Bibcode 1996PhRvD..53.5496F. doi:10.1103/PhysRevD.53.5496.
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- Government Reports on UFOs from UCB Libraries GovPubs
- CIA's Role in the Study of UFOs, 1947–90
- Ministry of Defence Reports in the UK from 1997 – 2007
- Newly released UFO files from the UK government
- "UFO, n.". OED Online. September 2012. Oxford University Press. 12 October 2012 <http://www.oed.com/view/Entry/208543?redirectedFrom=ufo&>.
- (Ruppelt, Report On Unidentified Flying Ojbects, Chapter 1)
- (FBI UFO files 1 of 16, p. 1-20)
- (Memorandum for the Officer In Charge, 1947)
- (Keyhoe, Flying Saucers from Outer Space, 1956)
- For example, the USAF's Project Blue Book concluded that less than 2 % of reported UFOs were "psychological" or hoaxes; Allen Hendry's study for CUFOS had less than 1 %
- Good, Timothy (1997). Beyond Top Secret. Pan Books.
- Cross, Anne (March, 2004). "The Flexibility of Scientific Rhetoric: A Case Study of UFO Researchers". Qualitative Sociology 27 (1): 3–34. doi:10.1023/B:QUAS.0000015542.28438.41.
- Sagan, Carl and Page, Thornton (1995). UFOs: A Scientific Debate. Barnes & Noble. p. 310. ISBN [[Special:BookSources/978076070916|978076070916]].
- McDonald, James. E. (1968). Statement on Unidentified Flying Objects submitted to the House Committee on Science and Astronautics at July 29, 1968, Symposium on Unidentified Flying Objects, Rayburn Bldg., Washington, D.D.
- COMETA Report: http://www.ufoevidence.org/topics/Cometa.htm
- Politicking and Paradigm Shifting: James E. McDonald and the UFO Case Study http://www.project1947.com/shg/mccarthy/shgintro.html
- UFO study causes media sensation: 7/1/98
- Menzel, D. H.; Taves, E. H. (1977). The UFO enigma. Garden City (NY, USA): Doubleday
- Vallée, J. (1990). Alien Contact by Human Deception." New York: Anomalist Books. ISBN 1-933665-30-0
- Giordano, Daniela, "Do UFOs Exist in the History of Arts?" from American Chronicle, November 13, 2006; retrieved July 27, 2007
- Cuoghi, Shaba. "The Art of Imagining UFOs". in Skeptic Magazine Vol.11, No.1, 2004. http://www.skeptic.com/the_magazine/archives/vol11n01.html.
- Before the Wright Brothers… There Were UFOs
- NAVY OFFICER SEES METEORS.; They Were Red Ones, the Largest About Six Suns Big. New York Times, March 9, 1904; Bruce Maccabee analysis, with original log entries of sighting; Maccabee summary of sighting with log quotes
-  NARCAP, 'Unidentified Aerial Phenomena: 80 Years of Pilot Sightings', "Catalog of Military, Airliner, Private Pilots’ Sightings from 1916 to 2000", Dominque F. Weinstein, 2003,
- Nicholas Roerich, 'Altai-Himalaya: A travel diary', Kempton, IL: Adventures Unlimited Press, 2001 (1929), pp. 361–2
- Nicholas Roerich, 'Shambhala: In search of the new era', Rochester, VE: Inner Traditions, 1990 (1930), pp. 6–7, 244., online
- Foo-Fighter – TIME
-  Hitler's Flying Saucers: Henry Stevens
- Project Blue Book Special Report #14
- For example, current USAF general reporting procedures are in Air Force Instruction (AFI)10-206. Section 5.7.3 (p. 64) lists sightings of "unidentified flying objects" and "aircraft of unconventional design" as separate categories from potentially hostile but conventional, unidentified aircraft, missiles, surface vessels, or submarines. Additionally, "unidentified objects" detected by missile warning systems, creating a potential risk of nuclear war, are covered by Rule 5E (p.35)
- Air Force Academy UFO material
- [dead link]
- "Official US Air Force document in pdf format". http://www.foia.af.mil/shared/media/document/AFD-070703-004.pdf. Retrieved November 12, 2007.
- "Wikisource article about Air Force Regulation 200-2". Archived from the original on May 5, 2008. http://web.archive.org/web/20080505013115/http://en.wikisource.org/wiki/Transwiki:Air_Force_Regulation_200-2. Retrieved November 12, 2007.
- Hynek, J. Allen. The UFO experience. Henry Regnery Company. , 1972, p. 76
- The Demon-Haunted World: Science as a Candle in the Dark
- Friedman, S. (2008). Flying Saucers and Science: A Scientist Investigates the Mysteries of UFOs. Franklin Lakes, NJ: New Page Books ISBN 978-1-60163-011-7
- Good (1988), 484
- George Kocher, UFOs: What to Do", RAND Corporation, 1968; UFO historical review, case studies, review of hypotheses, recommendations
- Many of these documents are now online at the FOIA websites of these agencies such as the FBI FOIA site, as well as private websites such as "The Black Vault", which has an archive[dead link] of several thousand U.S. government UFO-related documents from the USAF, Army, CIA, DIA, DOD, and NSA.
- Larson, Phil (5 November 2011). "Searching for ET, But No Evidence Yet". White House. https://wwws.whitehouse.gov/petitions#!/response/searching-et-no-evidence-yet. Retrieved 2011-11-06.
- Atkinson, Nancy (5 November 2011). "No Alien Visits or UFO Coverups, White House Says". UniverseToday. http://www.universetoday.com/90717/no-alien-visits-or-ufo-coverups-white-house-says/. Retrieved 2011-11-06.
- internal FBI memo from E. G. Fitch to D.M. Ladd concerning a request by General Schulgen of USAAF intelligence corps Office of Intelligence Requirements for the FBI to help with their investigation of UFO reports.
- Alfred Loedding and the Great Flying Saucer Wave of 1947, Sarah Connors and Michael Hall, White Rose Press, Albuquerque, 1998. Chapter 4: The Onslaught This quotes and summarized the interim report of Lieutenant Colonel George D. Garrett.
- The so-called Twining memo of Sept. 23, 1947, by future USAF Chief of Staff, Gen. Nathan Twining, specifically recommended intelligence cooperation with the Army, Navy, Atomic Energy Commission, the Defense Department's Joint Research and Development Board, Air Force Scientific Advisory Board, National Advisory Committee for Aeronautics (NACA), Project RAND, and the Nuclear Energy for the Propulsion of Aircraft (NEPA) project.
- Ruppelt, Chapt. 3
- https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/csi-studies/studies/97unclass/ufo.html CIA history of their involvement in UFOs
- See, e.g., the 1976 Tehran UFO incident where a Defense Intelligence Agency report on the event had a distribution list that included the White House, Secretary of State, Joint Chiefs of Staff, National Security Agency (NSA), and Central Intelligence Agency (CIA). Several thousand UFO-related pages of more recent vintage from the CIA, NSA, DIA, and other agencies have also been released and can be viewed online.
- McDonald, James E. (1972). "Science in Default". In Carl Sagan, Thornton Page. UFO's, A Scientific Debate. American Association for the Advancement of Science, 134th Meeting. Ithaca, New York: Cornell University Press. ISBN 978-0-393-00739-8. http://dewoody.net/ufo/Science_in_Default.html. Retrieved March 30, 2011.
- Ridge, Francis L.. "The Report on Unidentified Flying Objects". National Investigations Committee on Aerial Phenomena. http://www.nicap.dabsol.co.uk/Rufo.htm. Retrieved August 19, 2006.
- Canada's Unidentified Flying Objects: The Search for the Unknown, a virtual museum exhibition at Library and Archives Canada
- Site du GEIPAN
- Interview with GEIPAN director Yves Sillard; public statements of SEPRA director Jean-Jacques Velasco; 1978 GEPAN report by director Claude Poher.
- COMETA Report (English), part1; COMETA Report, part2; COMETA Report summary by Gildas Bourdais; Summary by Mark Rodeghier, director of CUFOS
- UK National Archives
- news.bbc.co.uk Files released on UFO sightings
- AFP Article: Britons 'spotted' UFOs, records say
- BBC News Airliner had near miss with UFO
- 'UAP In the UK Air Defense Region' Volume 3 Executive Summary, P. 2, August 2000
- 'The Black Vault', August 2009
- 'The Black Vault', August 2009
- "Cost-cutting causes British gov't to shut down UFO investigations"
- AFP: Churchill 'banned UFO report to avoid mass panic'
- Fox News: Churchill Ordered UFO Coverup, Documents Suggest
- BBC: Churchill ordered UFO cover-up, National Archives show
- The National Archives website
- 'El Pais', Montevideo,Uruguay, June 6, 2009; English translation by Scott Corrales
- Catalog of Project Blue Book unknowns
- Hynek's photos in Hynek, The UFO Experience, 1972, p. 52
- Herb/Hynek amateur astronomer poll results reprinted in International UFO Reporter (CUFOS), May 2006, pp. 14–16
- Electromagnetic-Wave Ducting [dead link] BY V. R. ESHLEMAN
- Allan Hendry, The UFO Handbook: A Guide to Investigating, Evaluating, and Reporting UFO Sightings, 1979, Doubleday & Co., ISBN 0-385-14348-6
- Armando Simon (1979). "The Zeitgeist of the UFO Phenomenon". UFO phenomena and the behavioral scientist (Scarecrow Press).
- Giere, Ronald N.; Bickle, John; Mauldin, Robert F. (2005), Understanding scientific reasoning (5th ed.), Wadsworth Publishing, p. 99, ISBN 0-15-506326-X
- UAP In the UK Air Defence Region: Volume 3 Executive Summary, Defence Intelligence Staff (2000), Page 3
- Sturrock Panel abstract & summary; Sturrock Panel report on physical evidence; Other links to Sturrock Panel
- Investigation and explanations of Belgium case
- Fawcett & Greenwood, 81–89; Good, 318–322, 497–502
- Good (1988), 371–373; Ray Stanford, Socorro 'Saucer' in a Pentagon Pantry, 1976, 112–154
- ibid; Oberth's UFO antigravity opinion as to propulsion and atmospheric air flow control also quoted by Donald Keyhoe in his 1955 book Flying Saucer Conspiracy
- Ika Krismantari, Crop circles provide food for thought, The Star, February 6, 2011
- bNet (CBS Interactive Inc.), "Is the Government Hiding Facts On UFOs & Extraterrestrial Life?; New Roper Poll Reveals that More Than Two-Thirds of Americans Think So,"  Last accessed February 2, 2008
- Poll: U.S. hiding knowledge of aliens, CNN/TIME, June 15, 1997
- Groupe d'Etudes et d'Informations sur les Phénomènes Aérospatiaux Non identifiés
- PARANOIA – People Are Strange: Unusual UFO Cults
- The Gulf Breeze "UFOs"
- "Warren Smith: UFO Investigator". http://www.middlecoastpublishing.com/ufo/warrenbillysmith.htm. Retrieved June 15, 2008.
- Bullard, 141
- "The Roper Poll". Ufology Resource Center. SciFi.com. September 2002. Archived from the original on July 13, 2006. http://web.archive.org/web/20060713204836/http://www.scifi.com/ufo/roper/. Retrieved August 19, 2006.
- CFI – Evidence Page
- Mutual UFO Network
- Astronomical Causes of UFOs
- Psychic Vibrations
- [dead link]