U. F. O. Writers
An unidentified flying object, or UFO, is any object in the air or upper atmosphere that cannot be identified. Some definitions, such as that which is used by the USAF, define a UFO as an object unable to be identified after scrutiny, while other definitions define an object as being a UFO from the time it is first reported as being unidentified, even though most subsequently become IFOs, Identified Flying Objects.
Reports of unusual aerial phenomena date back to ancient times, but modern reports and the first official investigations began during World War II with sightings of so-called foo fighters by Allied airplane crews, and in 1946 with widespread sightings of European "ghost rockets". UFO reports became even more common after the first widely publicized United States UFO sighting, by private pilot Kenneth Arnold in mid 1947. Hundreds of thousands of UFO reports have since been made worldwide.
Since its introduction the term has become heavily associated with flying saucers and alien spacecraft, though an object may be classified as a UFO independently of opinion as to its origins. Most military and civilian UFO investigations concluded that the majority of objects can be identified either directly, or by applying Occam's Razor.
On April 14, 1561 the skies over Nuremberg, Germany were reportedly filled with a multitude of objects. Woodcut from 1566 by Hans Glaser.Unusual aerial observations have been reported throughout history. Some were undoubtedly astronomical in nature: comets, bright meteors, one or more of the five planets which 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.
"The Baptism of Christ", 1710, by Aert de Gelder. Proponents say this painting depicts UFOs.Other historical reports seem to defy prosaic explanation, but assessing such accounts is difficult, because the information in a historical document may be insufficient, inaccurate, or embellished enough to make an informed evaluation difficult.
Whatever their actual cause, such sightings throughout history were often treated as supernatural portents, angels, or other religious omens. Art historian Daniela Giordano cites many Medieval-era paintings, frescoes, tapestries and other items that depict unusual aerial objects; she acknowledges many of these paintings are difficult to interpret, but cites some that depict airborne saucers and domed-saucer shapes that are often strikingly similar to UFO reports from later centuries. (See List of UFO sightings)
Shen Kuo (10311095), a Song Chinese government scholar-official and prolific polymath inventor and scholar, wrote a vivid passage in his Dream Pool Essays (1088) about an unidentified flying object. He recorded the testimony of eyewitnesses in 11th century Anhui and Jiangsu (especially in the city of Yangzhou), who stated that a flying object with opening doors would emit a blinding light from its interior (from an object shaped like a pearl) that would cast shadows from trees for ten miles in radius, and was able to take off at tremendous speeds.
 Pre-modern reports
Main article: List of UFO sightings
Photo of an unidentified object New Hampshire in 1870; known as the mystery airship.Before the terms "flying saucer" and "UFO" were coined in the late 1940s, there were a number of reports of unidentified aerial phenomena in the West. These reports date from the mid-nineteenth to early twentieth century. They include:
On January 25, 1878, The Denison Daily News wrote that local farmer John Martin had reported seeing a large, dark, circular flying object resembling a balloon flying "at wonderful speed."
On November 17, 1882, a UFO was observed by astronomer Edward Walter Maunder of the Greenwich Royal Observatory and some other European astronomers. Maunder in The Observatory reported "a strange celestial visitor" that was "disc-shaped", "torpedo-shaped", "spindle-shaped", or "just like a Zeppelin" dirigible (as he described it in 1916).
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.
Drawing of E. W. Maunder's Nov. 17, 1882, "auroral beam" by astronomer Rand Capron, Guildown Observatory, Surrey, UK, who also observed it.1916 and 1926: the three oldest known pilot UFO sightings, of 1305 catalogued by NARCAP. On January 31, 1916, a UK pilot near Rochford reported a row of lights, like 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 was forced to land by a huge, wingless cylindrical object.
On 5 August 1926, while traveling in the Humboldt Mountains of Tibet's Kokonor region, Nicholas Roerich reported that members of his expedition saw "something big and shiny reflecting sun, like a huge oval moving at great speed".
In both the European and Japanese aerial theatres during World War II, "Foo-fighters" (balls of light and other shapes that followed aircraft) were reported by both Allied and Axis pilots.
On February 25, 1942, the U.S. Army detected unidentified aircraft both visually and on radar over the Los Angeles, California region. No readily-apparent explanation was offered. The incident later became known as the Battle of Los Angeles, or the West coast air raid.
In 1946, there were over 2000 reports of unidentified aircraft in the Scandinavian nations, along with isolated reports from France, Portugal, Italy and Greece, then referred to as "Russian hail", and later as "ghost rockets", because it was thought that these mysterious objects were Russian tests of captured German V1 or V2 rockets. Over 200 were tracked on radar and deemed to be "real physical objects" by the Swedish military.
 The Kenneth Arnold sighting
Main article: Kenneth Arnold#June 24, 1947 UFO sighting
This shows the report Kenneth Arnold filed in 1947 about his UFO sighting.The post World War II UFO phase in the United States began with a reported sighting by American businessman Kenneth Arnold on June 24, 1947 while flying his private plane near Mount Rainier, Washington. He reported seeing nine brilliantly bright objects flying across the face of Rainier towards nearby Mount Adams at "an incredible speed", which he "calculated" as at least 1200 miles per hour by timing their travel between Rainier and Adams.
This shows Kenneth Arnold holding a picture of a drawing of the crescent shaped UFO he saw in 1947.His sighting subsequently received significant media and public attention. Arnold would later describe what he say as being "flat like a pie pan" and as flying "like a saucer would if you skipped it across the water" and also said they were and "half-moon shaped, oval in front and convex in the rear. ...they looked like a big flat disk." (One, however, he would describe later as being almost crescent-shaped.) Arnolds reported descriptions was widely reported upon and gave rise to the terms flying saucer and flying disk. Arnolds sighting was followed in the next few weeks by hundreds of other reported sightings, mostly in the U.S., but in other countries as well.
After reports of the Arnold sighting hit the media, other cases began to be reported in increasing numbers. In one instance a United Airlines crew sighting of nine more disc-like objects over Idaho on the evening of July 4. At the time, this sighting was even more widely reported than Arnolds and lent considerable credence to Arnolds report.
American UFO researcher Ted Bloecher, in his comprehensive review of newspaper reports, found a sudden surge upwards in sightings on July 4, peaking on July 68. Bloecher noted that for the next few days most American newspapers were filled with front-page stories of the new "flying saucers" or "flying discs". Reports began to tail off after July 8, when officials began issuing press statements on the now infamous Roswell UFO incident, in which they explained the debris as being that of a weather balloon.
Over several years in the 1960s, Bloecher (aided by physicist James E. McDonald) discovered 853 flying disc sightings that year from 140 newspapers from Canada, Washington D.C, and every U.S. state save Montana.
Main article: Ufology
Ufology is a neologism describing the collective efforts of those who study UFO reports and associated evidence. While not all UFO researchers believe that all UFOs are necessarily extraterrestrial spacecraft, they do believe the area merits research and that the possibility of extraterrestrial spacecraft should be taken seriously.
 Battelle Memorial Institute
An Air Force study by Battelle Memorial Institute scientists from 19521955 of 3200 USAF cases found 22% were unknowns, and with the best cases, 33% remained unsolved. Similarly about 30% of the UFO cases studied by the 1969 USAF Condon Committee were deemed unsolved when reviewed by the American Institute of Aeronautics and Astronautics (AIAA). The official French government UFO scientific study (GEIPAN) from 1976 to 2004 listed about 13% of 5800 cases as detailed yet inexplicable (with 46% deemed to have definite or probable explanations and 41% having inadequate information).
 UFO hypotheses
There are different opinions about the UFO phenomenon. To account for unsolved UFO cases, several hypotheses have been proposed by both proponents and skeptics; a few examples are given below:
Among proponents, some of the more common explanations for UFOs are:
The Extraterrestrial Visitation Hypothesis(ETH): That UFOs are alien spacecraft
The Interdimensional Hypothesis: That UFOs are the results of objects crossing over from other dimensions
The Paranormal/Occult Hypothesis
The hypothesis that they are time machines or vehicles built in a future time.
The man-made craft hypothesis: That UFOs are top secret Russian or American aircraft
Similarly, skeptics usually propose one of the following explanations:
The Psychological-Social Hypothesis
The unknown natural phenomena hypothesis, e.g. ball lightning, sprites
The Meteorological hypothesisPeter F Coleman advanced a meteorological theory that many UFOs or unexplained lights are actually instances of visible combustion of a fuel (e.g., natural gas) inside an atmospheric vortex. He has argued his case in his book, Great Balls of Firea unified theory. This vortex fireball theory was first published in Weather and later in the Journal of Scientific Exploration
The Earthquake lights/Tectonic Strain hypothesis
The Autokinetic effect hypothesis.
Other skeptical arguments against UFOs include:
Most UFO sightings are transitory events and there is usually no opportunity for the repeat testing called for by the scientific method.
Occam's razor of hypothesis testing, since it is considered less incredible for the explanations to be the result of known scientifically verified phenomena rather than resulting from novel mechanisms (e.g. the extraterrestrial hypothesis).
 UFO researchers
Main article: List of Ufologists
 UFO organizations
Main article: UFO organizations
 Physical evidence
Besides visual sightings, cases sometimes have indirect physical evidence, including many cases studied by the military and various government agencies of different countries. Indirect physical evidence would be data obtained from afar, such as radar contact and photographs. More direct physical evidence involves physical interactions with the environment at close rangeHynek's "close encounter" or Vallee's "Type-I" caseswhich include "landing traces," electromagnetic interference, and physiological/biological effects.
Radar contact and tracking, sometimes from multiple sites. These are often considered among the best cases since they usually involve trained 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 multiple 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, including some in the infrared spectrum (rare).
Recorded visual spectrograms (see Spectrometer)
Recorded gravimetric (example) and magnetic disturbances (extremely rare)
Landing physical trace evidence, including ground impressions, burned and/or desiccated soil, burned and broken foliage, magnetic anomalies, increased radiation levels, and metallic traces. See, e.g. Height 611 UFO Incident or the 1964 Lonnie Zamora's Socorro, New Mexico encounter, considered one of the most inexplicable of the USAF Project Blue Book cases). A well-known example from December 1980 was the USAF Rendlesham Forest Incident in England. Another less than two weeks later, in January 1981, occurred 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. Catalogs of several thousand such cases have been compiled, particularly by researcher Ted Phillips.
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. One such case dates back to 1886, a Venezuelan incident reported in Scientific American magazine.
So-called animal/cattle mutilation cases, that some feel are also part of the UFO phenomenon. Such cases can and have been analyzed using forensic science techniques.
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, including stalled cars, power black-outs, radio/TV interference, magnetic compass deflections, and aircraft navigation, communication, and engine disruption. A list of over 30 such aircraft EM incidents was compiled by NASA scientist Dr. Richard F. Haines. A famous 1976 military case over Tehran, recorded in CIA and DIA classified documents, resulted in 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. This was also a radar/visual case.
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.
Actual hard physical evidence cases, 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.
Misc: Recorded electromagnetic emissions, such as microwaves detected in the well-known 1957 RB-47 surveillance aircraft case, which was also a visual and radar case; polarization rings observed around a UFO by a scientist, explained by Dr. James Harder as intense magnetic fields from the UFO causing the Faraday effect.
These various reported physical evidence cases have been studied by various scientist and engineers, both privately and in official governmental studies (such as Project Blue Book, the Condon Committee, and the French GEPAN/SEPRA). A comprehensive scientific review of physical evidence cases was carried out by the 1998 Sturrock UFO panel.
 Reverse engineering
Attempts have been made to reverse engineer the possible physics behind UFOs through analysis of both eyewitness reports and the physical evidence. 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 of a microwave plasma parting the air in front of the craft is currently being researched by Dr. Leik Myrabo, Professor of Engineering Physics at the Rensselaer Polytechnic Institute as a possible advance in hypersonic flight. 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.
 Controversial cases
Among the many people who have reported UFO sightings, some have been exposed as hoaxers. Not all alleged hoax exposures are certain, however, and many claimants have stuck by their stories, leaving the determination of specific cases as hoaxes contentious. Some of the controversial subjects include these:
Bob White (UFO hunter) claims to have an alleged UFO artifact.
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 Jose Luis Jordan Pena came forward in the early nineties claiming responsibility for the phenomenon, and most 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.
In 1987 Ed Walters perpetrated a hoax in Gulf Breeze, Florida. Walters claimed at first having seen a small UFO flying near his home, and then in a second incident seeing the same UFO and a small alien being standing by his back door after being alerted by his dog. Several photographs were taken of the craft, but none of the being. 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. Various witnesses and detractors came forward after the local Pensacola newspaper printed a story about the discovered model, and some investigators now consider the sightings to be a hoax. In addition, a six-figure television miniseries and book deal were nearly struck with Walters.
Warren William (Billy) Smith, A popular writer and confessed hoaxster.
Some studies show that after investigation, the majority of UFOs are usually identified (see identified flying object). For example, a 1979 study by Allan Hendry, a UFO researcher dedicated to find evidence for extraterrestrial life, found that up to 91.4% of the reports he investigated were either identifiable (91.4%) or could possibly be attributable (7.1%) to known artificial objects and natural phenomena. Hendry's figure for unidentified cases is considerably lower than many official UFO studies such as Project Blue Book or the Condon Report which found unidentified cases made up 6% and 30% of reports respectively.
UFOs have been subject to various investigations over the years, varying widely in scope and scientific rigor. Governments or independent academics in the United States, Canada, the United Kingdom, France, Belgium, Sweden, Brazil, Mexico, Spain, and the Soviet Union are known to have investigated UFO reports at various times.
Among the best known government studies are 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 (19481951), and Brazilian Air Force Operation Saucer (1977). Major civilian UFO groups in the U.S that have conducted extensive investigations were/are NICAP, APRO, MUFON, and CUFOS.
 American investigations
Starting July 9, 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 Arnolds and the United crews. The AAF used "all of its scientists" to determine whether or not "such a phenomenon could, in fact, occur".[who?] 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, 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 thus recommended in late September 1947 that an official Air Force investigation be set up to investigate the phenomenon.
This led to the creation of the Air Forces Project Sign: One of the earliest government studies to come to a secret ETH conclusion, at the end of 1947, which became Project Grudge at the end of 1948, and then Project Blue Book In 1952. In 1948, they wrote a top-secret intelligence estimate to that effect. The Air Force Chief of Staff ordered it destroyed. The existence of this suppressed report was revealed by several insiders who had read it, such as astronomer and USAF consultant Dr. J. Allen Hynek and Edward J. Ruppelt, the first head of the USAF's Project Blue Book. (Ruppelt, Chapt. 3)
Blue Book closed down in 1970, ending the official Air Force UFO investigations. However, a 1969 USAF document, known as the Bolender memo, plus later government documents revealed that nonpublic U.S. government UFO investigations continued after 1970. The Bollender memo first stated that "reports of unidentified flying objects which could affect national security... are not part of the Blue Book system," indicating that more serious UFO incidents were already handled outside of 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."
An early U.S. Army study, of which little is known, was called the Interplanetary Phenomenon Unit (IPU). In 1987, British UFO researcher Timothy Good received a letter confirming the existence of the IPU from the Army Director of Counter-intelligence, in which it was stated, "...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.
Use of UFO instead of flying saucer was first suggested in 1952 by Capt. Edward J. Ruppelt, the first director of Project Blue Book, who felt that flying saucer did not reflect the diversity of the sightings. Ruppelt suggested that UFO should be pronounced as a word you-foe. However it is generally pronounced by forming each letter: U.F.O. His term was quickly adopted by the Air Force, which also briefly used "UFOB" circa 1954, for Unidentified Flying Object. Ruppelt recounted his experiences with Project Blue Book in his memoir, The Report on Unidentified Flying Objects (1956), also the first book to use the term.
Air Force Regulation 200-2, issued in 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." As with any then-ongoing investigation, Air Force personnel did not discuss the investigation with the press.
Well known American investigations include:
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 (19481951).
Ghost rockets investigations by the Swedish, U.K., U.S., and Greek militaries (19461947)
* The secret CIA Robertson Panel (1953)
The secret USAF Project Blue Book Special Report No. 14 by the Battelle Memorial Institute (19511954)
The Brookings Report (1960), commissioned by NASA
The public Condon Committee (19661968)
The private Sturrock Panel (1998)
 Canadian investigation
The Falcon Lake incident report filed by the Royal Canadian Mounted Police on Stephen Michalak claimed incident with a UFO.In 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 identifies the Falcon Lake incident in Manitoba and the Shag Harbour incident in Nova Scotia as "unsolved".
The Canadian studies include Project Magnet (19501954) and Project Second Story (19521954)
 French investigation
Wikinews has related news:
French Space Agency CNES releases UFO files
Pilots spot 'UFOs' near the Channel Islands
In 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, and the private French COMETA panel (19961999)
 British investigation
The UK conducted various investigations into UFO sightings and related stories. The contents of some of these investigations have since been released to the public.
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 is 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.
British investigations include The UK's Flying Saucer Working Party. Its final report, published in 1951, 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 delusions 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. Another notable investigation was Project Condign (19972000)
A secret study of UFOs undertaken for the UKs Ministry of Defence (MoD) between 1996 and 2000 and was publicly released in 2006. The report is titled "Unidentified Aerial Phenomena in the UK Defence Region" and was code-named Project Condign. 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." In contrast to the official government position, Nick Pope, the head of the UK government UFO desk for a number of years, is an advocate of the ETH, based on the inexplicable (to him) cases he reviewed, such as the Rendlesham UFO incident and the so-called Cosford Incident.
The 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 the 1970s, astrophysicist Peter A. Sturrock conducted two 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. In 1980, a survey of 1800 members of various amateur astronomer associations by Gert Helb and astronomer J. Allen Hynek of 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?"
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 Dr. 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. Even later UFO debunker Dr. Donald Menzel filed a UFO report in 1949.
Some studies were neutral in their conclusions, but argued the inexplicable core cases called for continued scientific study. Examples are the Sturrock Panel study of 1998 and the 1970 AIAA review of the Condon Report. Other private or governmental studies, some secret, have concluded in favor of the ETH, or have had members who disagreed with the official conclusions. The following are examples of such studies and individuals:
In 1967, Greek physicist Paul Santorini, a Manhattan Project scientist, publicly stated that a 1947 Greek government investigation that he headed into the European Ghost rockets of 1946 quickly concluded that they were not missiles. Santorini claimed the investigation was then quashed by military officials from the U.S., who knew them to be extraterrestrial, because there was no defense against the advanced technology and they feared widespread panic should the results become public.
November 1948 USAF Top Secret document citing extraterrestrial opinionA 1948 Top Secret USAF Europe document (at right) states that Swedish air intelligence informed them that at least some of their investigators into the ghost rockets and flying saucers concluded they had extraterrestrial origins: "...Flying saucers have been reported by so many sources and from such a variety of places that we are convinced that they cannot be disregarded and must be explained on some basis which is perhaps slightly beyond the scope of our present intelligence thinking. When officers of this Directorate recently visited the Swedish Air Intelligence Service... their answer was that some reliable and fully technically qualified people have reached the conclusion that 'these phenomena are obviously the result of a high technical skill which cannot be credited to any presently known culture on earth.' They are therefore assuming that these objects originate from some previously unknown or unidentified technology, possibly outside the earth."
West Germany, in conjunction with other European countries, conducted a secret study from 1951 to 1954, also concluding that UFOs were extraterrestrial. This study was revealed by German rocketry pioneer Hermann Oberth, who headed the study and who also made many public statements supporting the ETH in succeeding years. At the study's conclusion in 1954, Oberth declared, "These objects (UFOs) are conceived and directed by intelligent beings of a very high order. They do not originate in our solar system, perhaps not in our galaxy."
An FBI field office letter to the FBI Director, dated January 31, 1949, stated "...the matter of 'Unidentified Aircraft' or 'Unidentified Aerial Phenomena,' otherwise known as 'Flying Discs,' 'Flying Saucers,' and 'Balls of Fire' ...is considered Top Secret by Intelligence Officers of both the Army and Air Forces." (emphasis included in original).
During the height of the flying saucer "flap" of July 1952, including highly publicized radar/visual and jet intercepts over Washington, D.C., the FBI was informed by the Air Force Directorate of Intelligence that they thought the "flying saucers" were either "optical illusions or atmospheric phenomena" but then added that, "some Military officials are seriously considering the possibility of interplanetary ships."
The CIA started their own internal scientific review the following day. Some CIA scientists were also seriously considering the ETH. An early memo from August was very skeptical, but also added, "...as long as a series of reports remains 'unexplainable' (interplanetary aspects and alien origin not being thoroughly excluded from consideration) caution requires that intelligence continue coverage of the subject." A report from later that month was similarly skeptical but nevertheless concluded "...sightings of UFOs reported at Los Alamos and Oak Ridge, at a time when the background radiation count had risen inexplicably. Here we run out of even 'blue yonder' explanations that might be tenable, and we still are left with numbers of incredible reports from credible observers." A December 1952 memo from the Assistant CIA Director of Scientific Intelligence (O/SI) was much more urgent: "...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 highs speeds in the vicinity of U.S. defense installation are of such nature that they are not attributable to natural phenomena or known types of aerial vehicles." Some of the memos also made it clear that CIA interest in the subject was not to be made public, partly in fear of possible public panic. (Good, 331335)
The CIA organized the January 1953 Robertson Panel of scientists to debunk the data collected by the Air Force's Project Blue Book. This included an engineering analysis of UFO maneuvers by Blue Book (including a motion picture film analysis by Naval scientists) that had concluded UFOs were under intelligent control and likely extraterrestrial.
Extraterrestrial "believers" within Project Blue Book including Major Dewey Fournet, in charge of the engineering analysis of UFO motion. Director Edward J. Ruppelt is also thought to have held these views, though expressed in private, not public. Another defector from the official Air Force party line was consultant Dr. J. Allen Hynek, who started out as a staunch skeptic. After 20 years of investigation, he changed positions and generally supported the ETH. He became the most publicly known UFO advocate scientist in the 1970s and 1980s.
The first CIA Director, Vice Admiral Roscoe H. Hillenkoetter, stated in a signed statement to Congress, also reported in the New York Times, February 28, 1960, "It is time for the truth to be brought out... Behind the scenes high-ranking Air Force officers are soberly concerned about the UFOs. However, through official secrecy and ridicule, many citizens are led to believe the unknown flying objects are nonsense... I urge immediate Congressional action to reduce the dangers from secrecy about unidentified flying objects." In 1962, in his letter of resignation from NICAP, he told director Donald Keyhoe, "I know the UFOs are not U.S. or Soviet devices. All we can do now is wait for some actions by the UFOs."
Although the 1968 Condon Report came to a negative conclusion (written by Condon), it is known that many members of the study strongly disagreed with Condon's methods and biases. Most quit the project in disgust or were fired for insubordination. A few became ETH supporters. Perhaps the best known example is Dr. David Saunders, who in his 1968 book UFOs? Yes lambasted Condon for extreme bias and ignoring or misrepresenting critical evidence. Saunders wrote, "It is clear... that the sightings have been going on for too long to explain in terms of straightforward terrestrial intelligence. It is in this sense that ETI (Extra Terrestrial Intelligence) stands as the `least implausible' explanation of `real UFOs'."
Jean-Jacques Velasco, the head of the official French UFO investigation SEPRA, wrote a book in 2005 saying that 14% of the 5800 cases studied by SEPRA were utterly inexplicable and extraterrestrial in origin. Yves Sillard, the head of the new official French UFO investigation GEIPAN and former head of the French space agency CNES, echoes Velasco's comments and adds the U.S. is guilty of covering up this information. Again, this isn't the official public posture of SEPRA, CNES, or the French government. (CNES recently placed their 5800 case files on the Internet starting March 2007.)
The 1999 French COMETA committee of high-level military analysts/generals and aerospace engineers/scientists declared the ETH was the best hypothesis for the unexplained cases.
 National Press Club press conference on November 12, 2007
On November 12, 2007, Former Arizona Governor Fife Symington moderated a panel of former high-ranking government, aviation and military officials from seven countries at the National Press Club; discussing the UFO topic and governmental investigations. The press conference was open for credentialed media and congressional staff only.
 UFO categorization
Some researchers recommend that observations be classified according to the features of the phenomenon or object that are reported or recorded. Typical categories include:
Saucer, toy-top, or disk-shaped "craft" without visible or audible propulsion. (day and night)
Large triangular "craft" or triangular light pattern
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 system
Dr. J. Allen Hynek developed another system of description, dividing sightings into six categories.
It first separates sightings based on proximity, arbitrarily using 500 feet as the cutoff point. It then subdivides these into divisions based on viewing conditions or special features. The three distant sighting categories are:
Nocturnal Lights (NL): Anomalous lights seen in the night sky.
Daylight Discs (DD): Any anomalous object, generally but not necessarily "discoidal", seen in the distant daytime sky.
Radar/Visual cases (RV). Objects seen simultaneously by eye and on radar.
The distant classification is useful in terms of evidentiary value, with RV cases usually considered to be the highest because of radar corroboration and NL cases the lowest because of the ease in which lights seen at night are often confused with prosaic phenomena such as meteors, bright stars, or airplanes. RV reports are also fewest in number, while NL are largest.
In addition were three "close encounter" (CE) subcategories, again thought to be higher in evidentiary value, because it includes measurable physical effects and the objects seen up close are less likely to be the result of misperception. As in RV cases, these tend to be relatively rare:
CE1: Strange objects seen nearby but without physical interaction with the environment.
CE2: A CE1 case but creating physical evidence or causing electromagnetic interference (see below).
CE3: CE1 or CE2 cases where "occupants" or entities are seen. (Hence the title of Steven Spielberg's movie, Close Encounters of the Third Kind)
Hynek's CE classification system has since been expanded to include such things as alleged alien abductions (CE4s) and cattle mutilation phenomena.
 Vallee system
Jacques Vallee has devised a UFO classification system which is preferred by many UFO investigators over Hynek's system as it is considerably more descriptive than Hynek's, especially in terms of the reported behavior of UFOs.
Type I (a, b, c, d): Observation of an unusual object, spherical discoidal, or of another geometry, on or situated close to the ground (tree height, or lower), which may be associated with traces thermal, luminous, or mechanical effects.
On or near ground.
Near or over body of water.
Occupants appear to display interest in witnesses by gestures or luminous signals.
Object appears to be "scouting" a terrestrial vehicle.
Type II (a, b, c): Observation of an unusual object with vertical cylindrical formation in the sky, associated with a diffuse cloud. This phenomenon has been given various names such as "cloud-cigar" or "cloud-sphere."
Moving erratically through the sky.
Object is stationary and gives rise to secondary objects (sometimes referred to as "satellite objects").
Object is surrounded by secondary objects.
Type III (a, b, c, d, e): Observation of an unusual object of spherical, discoidal or elliptical shape, stationary in the sky.
Hovering between two periods of motion with "falling-leaf" descent, up and down, or pendulum motion.
Interruption of continuous flight to hover and then continue motion.
Alters appearance while hovering e.g., change of luminosity, generation of secondary object, etc.
"Dogfights" or swarming among several objects.
Trajectory abruptly altered during continuous flight to fly slowly above a certain area, circle, or suddenly change course.
Type IV (a, b, c, d): Observation of an unusual object in continuous flight.
Trajectory affected by nearby conventional aircraft.
Wavy or zig-zag trajectory.
Type V (a, b, c): Observation of an unusual object of indistinct appearance, i.e., appearing to be not fully material or solid in structure.
Extended apparent diameter, non-point source luminous objects ("fuzzy").
Starlike objects (point source), motionless for extended periods.
Starlike objects rapidly crossing the sky, possibly with peculiar trajectories.
Source: 1. Jacques and Janine Vallee: Challenge To Science: The UFO Enigma, LC# 66-25843
 Conspiracy theories
Main article: UFO conspiracy theory
UFOs are sometimes an element of elaborate conspiracy theories in which governments are said to be 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., opinion polls again indicate that a strong majority of people believe the U.S. government is 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).
There is also speculation that UFO phenomena are tests of experimental aircraft or advanced weapons. In this case UFOs are viewed as failures to retain secrecy, or deliberate attempts at misinformation: to deride the phenomenon so that it can be pursued unhindered. This explanation may or may not feed back into the previous one, where current advanced military technology is considered to be adapted alien technology (see also: skunk works and Area 51).
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 suppression
Some also contend regarding physical evidence that it exists abundantly but is swiftly and sometimes clumsily suppressed by governments, aiming to insulate a population they regard as unprepared for the social, theological, and security implications of such evidence. See the Brookings Report.
There have been allegations of suppression of UFO related evidence for many decades. There are also conspiracy theories which claim that physical evidence might have been removed and/or destroyed/suppressed by some governments. (See also Men in Black) Some examples are:
On July 7, 1947, William Rhodes took photos of an unusual object over Phoenix, Arizona. The photos appeared in a Phoenix newspaper and a few other papers. According to documents from Project Bluebook, an Army counter-intelligence (CIC) agent and an FBI agent interviewed Rhodes on August 29 and convinced him to surrender the negatives. The CIC agent deliberately concealed his true identity, leaving Rhodes to believe both men were from the FBI. Rhodes said he wanted the negatives back, but when he turned them into the FBI the next day, he was informed he wouldn't be getting them back, though Rhodes later tried unsuccessfully. The photos were extensively analyzed and would eventually show up in some classified Air Force UFO intelligence reports. (Randle, 3445, full account)
A June 27, 1950, movie of a "flying disk" over Louisville, Kentucky, taken by a Louisville Courier-Journal photographer, had the USAF Directors of counterintelligence (AFOSI) and intelligence discussing in memos how to best obtain the movie and interview the photographer without revealing Air Force interest. One memo suggested the FBI be used, then precluded the FBI getting involved. Another memo said "it would be nice if OSI could arrange to secure a copy of the film in some covert manner," but if that wasn't feasible, one of the Air Force scientists might have to negotiate directly with the newspaper. In a recent interview, the photographer confirmed meeting with military intelligence and still having the film in his possession until then, but refused to say what happened to the film after that.
In another 1950 movie incident from Montana, Nicholas Mariana filmed some unusual aerial objects and eventually turned the film over to the U.S. Air Force, but insisted that the first part of the film, clearly showing the objects as spinning discs, had been removed when it was returned to him. (Clark, 398)
During the military investigation of green fireballs in New Mexico, UFOs were photographed by a tracking camera over White Sands Proving Grounds on April 27, 1949. The final report in 1951 on the green fireball investigation claimed there was insufficient data to determine anything. However, documents later uncovered by Dr. Bruce Maccabee indicate that triangulation was accomplished. The data reduction and photographs showed four objects about 30 feet in diameter flying in formation at high speed at an altitude of about 30 miles. Maccabee says this result was apparently suppressed from the final report.
Project Blue Book director Edward J. Ruppelt reported that, in 1952, a U.S. Air Force pilot fired his jet's machine guns at a UFO, and that the official report which should have been sent to Blue Book was quashed.
Astronaut Gordon Cooper reported suppression of a flying saucer movie filmed in high clarity by two Edwards AFB range photographers on May 3, 1957. Cooper said he viewed developed negatives of the object, clearly showing a dish-like object with a dome on top and something like holes or ports in the dome. The photographers and another witness, when later interviewed by Dr. James McDonald, confirmed the story. Cooper said military authorities then picked up the film and neither he nor the photographers ever heard what happened to it. The incident was also reported in a few newspapers, such as the Los Angeles Times. The official explanation, however, was that the photographers had filmed a weather balloon distorted by hot desert air.
On January 22, 1958, when NICAP director Donald Keyhoe appeared on CBS television, his statements on UFOs were pre-censored by the Air Force. During the show when Keyhoe tried to depart from the censored script to "reveal something that has never been disclosed before," CBS cut the sound, later stating Keyhoe was about to violate "predetermined security standards" and about to say something he wasn't "authorized to release." What Keyhoe was about to reveal were four publicly unknown military studies concluding UFOs were interplanetary (including the 1948 Project Sign Estimate of the Situation and Blue Book's 1952 engineering analysis of UFO motion). (Good, 286287; Dolan 293295)
Astronomer Jacques Vallee reported that in 1961 he witnessed the destruction of the tracking tapes of unknown objects orbiting the Earth. (However, Vallee indicated that this didn't happen because of government pressure but because the senior astronomers involved didn't want to deal with the implications.)
In 1965, Rex Heflin took four Polaroid photos of a hat-shaped object. Two years later (1967), two men posing as NORAD agents confiscated three prints. Just as mysteriously, the photos were returned to his mailbox in 1993.
A March 1, 1967 memo directed to all USAF divisions, from USAF Lt. General Hewitt Wheless, Assistant Vice Chief of Staff, stated that unverified information indicated that unknown individuals, impersonating USAF officers and other military personnel, had been harassing civilian UFO witnesses, warning them not to talk, and also confiscating film, referring specifically to the Heflin incident. AFOSI was to be notified if any personnel were to become aware of any other incidents. (Document in Fawcett & Greenwood, 236).
John Callahan, former Division Chief of the Accidents and Investigations Branch of the FAA, Washington D.C., also a Disclosure Project witness, said that following a 1986 encounter of a Japanese airlines 747 with a giant UFO over Alaska, recorded by air and ground radar, the FAA conducted an investigation. Callahan held a briefing a few days later for President Reagan's Scientific Study Group, the FBI, and CIA. After the briefing, one of the CIA agents told everybody they "were never there and this never happened," adding they were fearful of public panic.
In 1996, the CIA revealed an instance from 1964 where two CIA agents posed as USAF representatives in order to recover a film canister from a Corona spy satellite that had accidentally come down in Venezuela. The event was then publicly dismissed as an unsuccessful NASA space experiment.
 UFOs in popular culture
Main article: UFOs in Fiction
UFOs constitute a widespread international cultural phenomenon of the last half-century. 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 US President Gerald Ford in a 1977 poll taken just nine months after he left the White House. (Bullard, 141) 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 UFOs were 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. Another effect of the flying saucer type of UFO sightings has been Earth-made flying saucer craft in space fiction, for example the Earth-made craft Starship C-57D in Forbidden Planet, and the saucer part of the USS Enterprise in Star Trek.
 Use in film and television