Ufology (pronounced /juːˈfɒlədʒɪ/) is a neologism coined to describe the collective efforts of those who study unidentified flying object reports and associated evidence. While Ufology does not represent an academic research program, UFOs have been subject to various investigations over the years. 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. Perhaps the best known study was Project Blue Book, previously Project Sign and Project Grudge, conducted by the United States Air Force from 1947 until 1969. Other notable investigations include the Robertson Panel (1953), the Brookings Report (1960), the Condon Committee (1966–1968), the Project Twinkle investigation into green fireballs (1948–1951), the Sturrock Panel (1998), and the French GEIPAN (1977-) and COMETA (1996–1999) study groups. However, no national government has ever officially and publicly asserted that UFOs represent any form of alien intelligence.
Background and status as a field
Ufology has never been fully embraced by academia as a scientific field of study even though it was, in the early days, the subject of large scale scientific studies that produced reports described to follow. Prior to August, 2008, one could not obtain a "ufology" degree from any college or university, though there have been a few college or university courses on the subject, often from a folklore perspective.
Ufologists vary from proponent David Icke to scientists like Peter A. Sturrock, J. Allen Hynek, Jacques Vallee, James E. McDonald, or Auguste Meessen, some of whom argue that UFO reports are as worthy of study as any topic, and deserve case-by-case analysis using the scientific method. Debunkers include Philip Klass and Dr. Donald Menzel.
Not all ufologists believe that UFOs are necessarily extraterrestrial spacecraft, or even that they are objective physical phenomena. Even those UFO cases that are exposed as hoaxes, or found to be delusions or misidentifications may still be worthy of serious study from a psychosocial point of view.
Dr. Carl Sagan was quite skeptical of any extraordinary answer to the UFO question, but in 1969, he co-organised a symposium on the subject, thinking that science had unfairly neglected the UFO question. However, Westrum wrote that "Sagan spent very little time researching UFOs...he thought that little evidence existed to show that the UFO phenomenon represented alien spacecraft and that the motivation for interpreting UFO observations as spacecraft was emotional." Sagan's college classmate Stanton T. Friedman criticized Sagan for ignoring evidence, such as "600-plus UNKNOWNS of Project Blue Book Special Report No. 14." Friedman refers to a table in Project Blue Book Special Report No. 14 that he says "shows that the better the quality of the sighting, the more likely it was to be an 'unknown,' and the less likely it was to be listed as 'insufficient information'"  (p. 42). Friedman argued that this empirical data directly contradicts Sagan's claim in Other Worlds, that the "reliable cases are uninteresting and the interesting cases are unreliable. Unfortunately there are no cases that are both reliable and interesting."
In her critique of the Condon Report, Diana Palmer Hoyt notes that:
“The UFO problem seems to bear a closer resemblance to problems in meteorology than in physics. The phenomena are observed, occur episodically, are not reproducible, and in large part, are identified by statistical gathering of data for possible organization into patterns. They are not experiments that can be replicated at will at the laboratory bench under controlled conditions.”
Along these lines, Peter A. Sturrock suggests that UFO studies should be compartmentalized—as are most scientific endeavors—into at least "the following distinct activities:"
1. Field investigations leading to case documentation and the measurement or retrieval of physical evidence; 2. Laboratory analysis of physical evidence; 3. The systematic compilation of data (descriptive and physical) to look for patterns and so extract significant facts; 4. The analysis of compilations of data (descriptive and physical) to look for patterns and so extract significant facts; 5. The development of theories and the evaluation of those theories on the basis of facts.
Study of UFO sightings has yielded results applicable to other fields, such as in weather phenomena and in human perception, such as the study lead by the SOBEPS for the Belgian flap in 1989-90 or the studies of the GEPAN/SEPRA in France.
The lack of acceptance of ufology by mainstream academia as a field of study means that people can claim to be "UFO researcher", without the sorts of scientific consensus building and, in many cases peer review, that otherwise shape and influence scientific paradigms. This has allowed many to stake out territory and disseminate claims, information and analysis of widely varying rigor and quality.
Some ufologists, such as Stanton Friedman (2008), consider the general attitude of mainstream academics as arrogant and dismissive, or bound to a rigid world view that disallows any evidence contrary to previously held notions. Others charge that mainstream rejection of UFO evidence is a classic case of pathological science. Astronomer and ufologist J. Allen Hynek's famous comment regarding this subject is, "Ridicule is not part of the scientific method and people should not be taught that it is." Another comment by Hynek regarding the frequent dismissal of UFO reports by astronomers was, "Close questioning revealed they knew nothing of the actual sightings, of their frequency or anything much about them, and therefore cannot be taken seriously. This is characteristic of scientists in general when speaking about subjects which are not in their own immediate field of concern."
Critics like Robert Sheaffer have accused ufology of having a "credulity explosion." He claims a trend of increasingly sensational ideas steadily gaining popularity within ufology. Sheaffer remarked "the kind of stories generating excitement and attention in any given year would have been rejected by mainstream ufologists a few years earlier for being too outlandish."
Whether or not this view has a basis in evidence, James McDonald long ago expressed the view that extreme groups undermined serious scientific investiation, stating that a "bizarre "literature" of pseudo-scientific discussion" on "spaceships bringing messengers of terrestrial salvation and occult truth" had been "one of the prime factors in discouraging serious scientists from looking into the UFO matter to the extent that might have led them to recognize quickly enough that cultism and wishful thinking have nothing to do with the core of the UFO proglem." In the same statement, McDondald said that :
"Again, one must here criticize a good deal of armchair-researching (done chiefly via the daily newspapers that enjoy feature-writing the antics of the more extreme of such subgroups). A disturbing number of prominent scientists have jumped all too easily to the conclusion that only the nuts see UFOs." 
The Air Force's Project Blue Book files indicate that approximately 1% of all their 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 6 UFO sightings, including 3 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 2 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 .
Physicists and UFOs
Certain physicists, some working for the US Military, others said to be associated with the US Intelligence Community are seriously interested in UFOs as extraterrestrial flying machines. Dr. Jack Sarfatti, in his book "Super Cosmos" (2005), has an extremely detailed "theory" based on the recent discovery of the repulsive anti-gravity field "dark energy" that is accelerating the expansion of the 3D space of our universe. Sarfatti also cites Alcubierre's weightless warp drive without time dilation as essential conditions for "propellantless propulsion" in what Puthoff has called "metric engineering." In his book "The Physics of Star Trek," Lawrence M. Krauss argues that it would be physically impossible to concentrate enough energy in one place to "warp" the fabric of space.
According to other physicists, taking advantage of certain experimentally verified quantum phenomena, such as the Casimir effect, may make the construction of Alcubierre type warp drives theoretically possible. However, if certain quantum inequalities conjectured by Ford and Roman (1996) hold, then the energy requirements for some warp drives may be absurdly gigantic, e.g. the energy -1067g might be required to transport a small spaceship across the Milky Way galaxy. Counterarguments to these apparent problems have been offered (Krasnikov, 2003), but not all physicists are convinced they can be overcome. (For a detailed discussion, see: Alcubierre drive.)
Various public scientific studies over the past half century have examined UFO reports in detail. None of these studies have officially concluded that any reports are caused by extraterrestrial spacecraft (e.g., Seeds 1995:A4). 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:
- One of the earliest government studies to come to a secret ETH conclusion was Project Sign, the first official Air Force UFO investigation. 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)
- 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. 
- 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. 
- A 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." 
- Various European countries conducted a secret joint study in 1954, also concluding that UFOs were extraterrestrial. This study was revealed by German rocketry pioneer Hermann Oberth, a member of the study, who also made many public statements supporting the ETH.
- In 1958, Brazil's main UFO investigator, Dr. Olavo T. Fuentes wrote a letter to the American UFO group APRO summarizing a briefing he had received from two Brazilian Naval intelligence officers. Fuentes said he was told that every government and military on Earth was aware that UFOs were extraterrestrial craft and there was absolute proof of this in the form of several crashed craft. The subject was classified Top Secret by the world's militaries. The objects were deemed dangerous and hostile when attacked, many planes had been lost, and it was generally believed that Earth was undergoing an invasion of some type, perhaps a police action to keep us confined to the planet. This information had to be withheld from the public by any means necessary because of the likelihood of widespread panic and social breakdown. 
- During the height of the flying saucer epidemic 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." FBI document
- 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,331-335)
- 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'." 
- Nick Pope, a Higher Scientific Officer in the UK MOD who was responsible for the UK government UFO desk for a number of years, is an advocate of the ETH based on the inexplicable cases he reviewed, such as the Rendlesham UFO incident, although the British government has never made such claims.
- 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 announced that their 5800 case files will be placed 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. 
Besides visual sightings, UFO cases sometimes involves direct or indirect physical evidence. Reports of these are often included in studies by the military and various government agencies. Direct physical evidences are rare, and involve actual artifacts coming from the UFO; indirect evidence, on the other hand, would be data obtained from afar, such as radar contact and photographs. More direct physical evidence involves physical interactions with the environment at close range—Hynek's "close encounter" or Vallee's "Type-I" cases—which include "landing traces," electromagnetic interference, and physiological/biological effects.
- 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. Another example of possible physical evidence is the "Bob White object" a strange feather shaped object supposedly recovered by Bob White in 1985. The object was featured in the popular UFO show UFO Hunters 
- 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 2 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.
- 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)
- 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 (extremely rare) — (see Spectrometer)
- Recorded gravimetric and magnetic disturbances (extremely rare)
- 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.
- 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. (Fawcett & Greenwood, 81-89; Good, 318-322, 497-502)
- 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.
- 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.
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 online, 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.1995 Aviation Week article
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)
- Rapidly-moving lights or lights with apparent ability to rapidly change direction and then suddenly stop, impossible for conventional aircraft.
- Large triangular “craft” or triangular light pattern
- Cigar-shaped “craft” with lighted windows (Meteor fireballs are sometimes reported this way).
- Other: chevrons, equilateral triangles, spheres, domes, diamonds, shapeless black masses, eggs, and cylinders.
J. Allen Hynek developed another commonly used system of description, dividing sightings into six categories. It first separates sightings into distant- and close-encounter categories, arbitrarily setting 500 feet as the cutoff point. It then subdivides these close and distant categories based on appearance or special features. The three distant-encounter 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.
Subgroups of the distant category of sightings correlate with evidentiary value. RV cases are usually considered to have the highest value because of radar corroboration, whereas NL cases have the lowest because it is so easy to mistake lights seen at night for prosaic phenomena such as meteors, bright stars, or aircraft. RV reports are also fewest in number, while NL are most common.
Hynek also defined three “close encounter” (CE) subcategories:
- CE1: Strange objects seen nearby but without physical interaction with the environment.
- CE2: A CE1 case that leaves physical evidence (e.g. soil depressions, vegetation damage) or causes 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.)
From UFO Casebook
- CE4+: aliens communicate with the observer, even abduct, experiment on the observers, others. UFO Casebook lists additional categories, in which the UFO and/or alien is captured/destroyed by military forces and/or civilians.
Like the RV cases, CE cases are considered higher in evidentiary value because they include measurable physical effects, and because objects seen up close are less likely to be the result of misperception. Like the RV cases, these tend to be relatively rare.
Hynek’s CE classification system has since been expanded to include such things as alleged alien abductions and cattle mutilation phenomena.
Jacques Vallée 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.
- a - On or near ground.
- b - Near or over body of water.
- c - Occupants appear to display interest in witnesses by gestures or luminous signals.
- d - 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.”
- a - Moving erratically through the sky
- b - Object is stationary and gives rise to secondary objects (sometimes referred to as “satellite objects”)
- c - 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.
- a - Hovering between two periods of motion with “falling-leaf” descent, up and down, or pendulum motion
- b - Interruption of continuous flight to hover and then continue motion
- c - Alters appearance while hovering - e.g., change of luminosity, generation of secondary object, etc.
- d - “Dogfights” or swarming among several objects
- e - 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.
- a - Continuous flight
- b - Trajectory affected by nearby conventional aircraft
- c - Formation flight
- d - 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.
- a - Extended apparent diameter, non-point source luminous objects (“fuzzy”)
- b - Starlike objects (point source), motionless for extended periods
- c - Starlike objects rapidly crossing the sky, possibly with peculiar trajectories 
Astrophysicist Peter A. Sturrock suggests that a lack of funding is a major factor in the institutional disinterest in UFO’s: "If the Air Force were to make available, say, $50 million per year for ten years for UFO research, it is quite likely that the subject would look somewhat less disreputable ... however, an agency is unlikely to initiate such a program at any level until scientists are supportive of such an initiative. We see that there is a chicken-and-egg program. It would be more sensible, and more acceptable to the scientific community, if research began at a low level." 
These hypotheses speculate that the phenomena derives wholly or in part from a phenomenon, rather than the mind of the observer.
The extraterrestrial hypothesis
The extraterrestrial hypothesis (ETH) theorizes that some UFO sightings are alien spacecraft.
The staging hypothesis
A sub-set of the ETH, the Staging Hypothesis, prevalent up until the 1980s, speculated that extraterrestrials have "stage-managed" encounters as a deliberate policy to "educate" humanity.
The hostility hypothesis
Wilhelm Reich and Jerome Eden have the hypothesis that UFOs - or at least some of them - or the beings traveling in the UFOs - are hostile. They claim that the waste product of the UFO engines is what they call "Deadly Orgone" (DOR) which ruins the atmosphere, dries it out, and is one cause, if not the most important cause, of the development of deserts. They found this during their operations with the "Cloudbuster".
Eden, just like several other researchers, attributes the Cattle mutilations, cases such as "Snippy the horse", to aliens, and claims that these beings abduct persons, manipulate their feelings and thoughts, cause military aircraft to crash or disappear, but they do not make open contact to government or military. That they even try to "educate" mankind in the way that the human beings develop a spiritual attitude towards aliens and UFOs, hoping that the aliens arrive as the saviors for the big problems of mankind and earth, when, in fact, their agenda involves exploiting Earth's natural resources and destroying its water and atmosphere.
The advanced human aircraft hypothesis
This is a theory that all or some UFO sightings are advanced, secret or experimental aircraft of earthly origin.
- During the 1980s, there were reports of "black triangle" UFOs. Some of these were the secret F-117 Nighthawk, which became known to the public in November 1988.
- Nazi Germany is known to have experimented with circular jet planes using the Coanda effect. At least one of the scientists involved was taken to the USA after WWII. Experiments with these designs and their descendants down the years may explain many sightings of circular UFO's.
Military flying saucers
There is a theory that the secret groups developing these aircraft in the USA, have been encouraging ufology to follow the Extraterrestrial hypothesis line of thought, to cover up for sightings.
The Cosmic Trickster and Ultraterrestrial hypothesis
Endorsed by John Keel (who coined the term "ultraterrestrial"), Jacques Vallée in his Passport to Magonia, Robert Anton Wilson and Terence McKenna, this theory claims that UFO's have an objective reality, though of a kind humans cannot comprehend or understand.
A frequent sub-set of this theory conjectures that in the past the ultimate reality behind UFO's manifested as angels, demons, fairies and other "supernatural" beings. This over-laps both with the Staging Hypothesis and the Psychosocial Hypothesis.
Time travel or parallel worlds
Alternately, UFO's are craft that come from a parallel dimension or similar, or are human-manufactured craft from the future capable of time travel.
The "critter" or "sky beast" hypothesis
The theory of Trevor James Constable speculated that UFO sightings involve the sighting of exotic unknown life otherwise known as "Critters" or "Heat Critters". This theory seems to have some connections to Constable's interpretations on Wilhelm Reich's Orgone energy, a concept that has very little support by psychologists, and none by other scientists.
- UFO's as supernatural beings
- UFOs as perception or illusion
- The mistaken observer hypothesis
This is a theory that most UFO sightings are misunderstood phenomena such as ball lightning or visual illusions. See Identified Flying Objects (IFOs).
Carl G. Jung, the Swiss psychoanalyst, in his 1957 work, Flying Saucers: A Modern Myth of Things Seen in the Skies, explained UFOs as objects of the collective unconscious and modern archetypes. Paradoxically, in a brief final chapter of his book, Jung also expressed his opinion that some UFOs were real "nuts-and-bolts" craft, citing corroborating physical evidence.
In psychology, the study of UFO sightings has revealed information on misinterpretation, perceptual illusions, hallucination. Many have questioned the reliability of hypnosis in UFO abduction cases..
UFO-related claims that are based solely on eyewitness accounts are subject to a range of issues that may be involved with eyewitness memory. Under some circumstances, eyewitness memory is unreliable. In addition, there is some evidence that memory of an event can be unconsciously altered to suit a desired interpretation of what was remembered. For example, it is possible a person who has reported a UFO sighting may be reinterpreting an older memory to fit a desired explanation. One study has reported that participants who reported recovered memories of abduction by aliens were more prone than a control group to exhibit false recall.  However, the authors note as a limitation, that a small sample size was used in the study. In addition, the study did not address the alternative hypothesis that only a subgroup of those who reported abductions could account for the observed differences; i.e. it is possible some of the group claiming abduction were more prone to false recall while others were not.
The Psychosocial Hypothesis, advocated in the early work of Hilary Evans, posits that some UFO sightings are hallucinations or fantasies and are caused by the same mechanism as various occult, paranormal, supernatural or religious experiences (compare alleged sightings of the Blessed Virgin Mary).
The Tectonic Strain and electro-staging theories
A number of theorists have concluded that, jointly, Earthlight lights (a somewhat disputed phenomenon within the mainstream scientific community) and the effect of natural (and in some cases artificial electromagnetic radiation) causes altered states of consciousness.
- United States Air Force Project Blue Book: Small, public Air Force UFO investigation, from 1952 until discontinued in 1969. Preceded by Project Sign (1947–1948) and Project Grudge (1948–1952).
- Aerial Phenomena Research Organization (APRO) (1952–1988): Early, national U.S. civilian research organization with many PhD consulting scientists.
- National Investigations Committee On Aerial Phenomena (NICAP)(1956–1980), Early, national U.S. civilian research organization, very large and powerful at one time, with many scientists and military consultants.
- Mutual UFO Network (MUFON): Large, international, U.S. based civilian research organization stressing field investigations and data collection. MUFON is the largest civilian UFO research group in the United States today.
- Center for UFO Studies (CUFOS): Founded by Project Blue Book consultant, astronomer and ufologist J. Allen Hynek; stresses scientific investigations; large archives, including old NICAP files.
- Fund for UFO Research: Funds scientific UFO research; many consulting PhD scientists; does photoanalysis.
- National Institute of Discovery Science (NIDS): Private, somewhat clandestine organization with insider government scientists and military people stressing scientific forensic analysis of UFO and paranormal phenomena.
- Phenomena Research Australia (PRA): This group has grew out of the Aeronautical Research Laboratory – Melbourne, Victoria c1949.
- Committee for the Scientific Investigation of Claims of the Paranormal, (CSICOP), a UFO and paranormal skeptics organization, which classifies ufology as a pseudoscience and claims all UFO reports are ultimately explainable as mundane phenomena or hoaxes. CSICOP is the largest and most prominent group of UFO skeptics and debunkers in the United States.
- UFO-Norge, a Norwegian project dedicated to collect all material on observations and physical traces of UFO activity in Norway.
- Erich von Däniken's controversial theories (along with Peter Kolosimo), where he combines what he considers historical proof of extraterrestrial visits with a theory on extraterrestrial help in the evolution of humanity.
- SOBEPS: Société Belge d'Etude des Phénomènes Spatiaux(1971–2007). This group gained fame to have investigated the Belgian Wave (see Black triangle incidents).
- Karla Turner
- Disclosure Project
Panel discussion 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.
- Sergey Litsak, Explanatory UFO Dictionary with Equivalents in Russian, English and German. ETS Publishing House and Polyglossum, Inc; ISBN 5-86455-063-9. Dictionary contains 853 articles.
- Roth, Christopher F., "Ufology as Anthropology: Race, Extraterrestrials, and the Occult." In E.T. Culture: Anthropology in Outerspaces, ed. by Debbora Battaglia. Durham, N.C.: Duke University Press, 2005.
- Peter A. Sturrock; The UFO Enigma: A New Review of the Physical Evidence; Warner Books, 1999; ISBN 0-446-52565-0
- Jerome Eden; "The Desert Makers", Careywood, Idaho, PPCC, 1981, available from Flatlandbooks.
- Jerome Eden; "Scavengers From Space", Careywood, Idaho, PPCC, 1989, at present time out of print.
- Why SETI Is Science and UFOlogy Is Not - A Space Science Perspective on Boundaries, Mark Moldwin, 2004
- A degree in strange flying objects alien no longer, Sydney Morning Herald, August 5, 2008
- Westrum, Ron; Jacobs, David Michael (ed.) (2000). "Limited Access: Six Natural Scientists and the UFO Phenomenon." UFOs and abductions: Challenging the Borders of Knowledge. Lawrence, Kansas: University Press of Kansas. pp. 30–55. ISBN 0700610324.
- 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
- Sturrock, 163
- Hynek, Josef Allen (April 1953). "Unusual Aerial Phenomena". Journal of the Optical Society of America 43 (4): 311–314. doi:10.1364/JOSA.43.000311.
- Josef Allen Hynek (1952-08-06). Special report on conferences with astronomers on unidentified aerial objects. NARA. .
- Sheaffer, Robert. "A Skeptical Perspective on UFO Abductions." In: Pritchard, Andrea & Pritchard, David E. & Mack, John E. & Kasey, Pam & Yapp, Claudia. Alien Discussions: Proceedings of the Abduction Study Conference. Cambridge: North Cambridge Press. Pp. 382-388.
- name = McDonald
- 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.
- Herb/Hynek amateur astronomer poll results reprinted in International UFO Reporter (CUFOS), May 2006, pp. 14-16
- "Pdf document on UFOs and Clyde Tombaugh" (PDF). . Retrieved on 2008-01-12.
- Full quote in Clyde Tombaugh article; originally  and 
- "Menzel's sighting". .
- Cramer, John G.. "NASA Goes FTL Part 1: Wormhole Physics". .
- Visser, Matt; Sayan Kar, Naresh Dadhich (2003). "Traversable wormholes with arbitrarily small energy condition violations". Physical Review Letters 90: 201102.1–201102.4. doi:10.1103/PhysRevLett.90.201102. arΧiv:gr-qc/0301003
- Good (1988), 484
- Good (1988), 23
- Document quoted and published in Timothy Good (2007), 106-107, 115; USAFE Item 14, TT 1524, (Top Secret), 4 November 1948, declassified in 1997, National Archives, Washington D.C.
- Good (1988), 426-427; excerpt from Fontes letter
- Dolan, 189; Good, 287, 337; Ruppelt, Chapt. 16
- Good, 347
- 1960s Condon Report A Whitewash
- 'Yes, UFOs exist': Position statement by SEPRA head, Jean-Jacques Velasco - UFO Evidence
- Official French Gov't UFO study project to resume with new director - UFO Evidence
- USA: UFOs and National Security - UFO Evidence
- Trans-en-Provence Physical Trace Case - Trans-en-Provence, France - January 8, 1981 - UFO Evidence
- Chapter Thirteen:The Report On Unidentified Flying Objects
- UFO Evidence : Physical Trace Cases
- Top Physical Trace Cases - Cases of High Strangeness - A Preliminary List - UFO Evidence
- Best UFO Cases III: Belgium, 1989-1990 - UFO Evidence
- UFO Evidence : JAL Flight 1628 Over Alaska
- Letter to Scientific American, Dec 18, 1886
- UFO Evidence : Electromagnetic Effects
- Tehran, Iran/ F-4 Incident
- Iranian Jet Case
- ufo - UFOS at close sight: Blue Book's Captain Ruppelt's book, chapter 15, the radiation story
- ufo - UFOS at close sight: RB-47 radar visual multiple witnesses cases, July 17, 1957
- UFO Symposium 1968: Harder Statement
- Table of Contents for "Physical Evidence Related to UFO Reports"
- Myrabo, Leik N
- Jacques and Janine Vallee: Challenge To Science: The UFO Enigma, LC# 66-25843
- Sturrock, 155
- See also Wilhelm Reich#Orgone accumulators and cloudbusters
- Snippy the Horse -the Most Famous Horse in the World! official website
- "The cosmic pulse of life", by Trevor Constable
- burlingtonnews.net: UFOs OVER BURLINGTON WISCONSIN
- Eyewitness memory in context: toward a systematic understanding
- Today@UCI: Press Releases:
- "Reuters news article concerning the press conference". .
- "ABC News West Palm Beach video file on the press conference". .
- "CNN article about the press conference". .
- "AFP via Yahoo article about the press conference". .
- "BBC article concerning the press conference". 
- "Full video taken during the press conference". .