thumb|alt=An ad reads, "Why were these men silenced? They Knew Too Much About Flying Saucers"|1956 advertisement, formatted similar to a newspaper article, for the book [[They Knew Too Much About Flying Saucers which promoted a conspiracy theory that government agents were silencing UFO witnesses (Los Angeles Times, June 24, 1956).]]
Some conspiracy theories argue that various governments and politicians globally, in particular the United States government, are suppressing evidence that unidentified flying objects (UFO) are controlled by an extraterrestrial or "non-human" intelligence, or built using alien technology. Since the 1980s, such conspiracy theories often argue that world governments are in communication or cooperation with extraterrestrials, and some claim that the governments are explicitly allowing cattle mutilation and alien abduction.
Mainstream scientists, government investigators, and skeptics maintain that little or no evidence exists to support conspiracy theories regarding alien visitation. Despite claims of cover-ups, conspiracy theories about alien spaceships largely lack verifiable proof, relying instead on speculation, anecdotes, and misidentified surveillance technology.
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Flying saucer conspiracy theories first began in the pages of pulp science-fiction, where they drew upon inspiration from the "lost continent" myths of Atlantis and Lemuria. In 1947, during 'the first summer of the cold war', private pilot Kenneth Arnold reported witnessing supersonic 'flying discs'; historians would later chronicle at least 800 "copycat" reports in subsequent weeks, while other sources estimate the reports may have numbered in the thousands. Press speculated that the flying discs were secret American or Soviet technology.
By December 1949, author Donald Keyhoe promoted the idea that the Air Force was withholding knowledge of interplanetary spaceships, culminating in his 1955 work The Flying Saucer Conspiracy. The following year, the book They Knew Too Much About Flying Saucers introduced the concept of the Men in Black.
While earlier decades imagined a cover-up of benevolent "space brothers", the 1980s saw the rise of what scholars called "ufology's dark side": theories that a government cabal was secretly involved with a race of malevolent aliens.
In 2017, UFO conspiracy theories experienced renewed interest when Leslie Kean published stories of a 21st-century Pentagon UFO program.
Mainstream views
While unusual sightings have been reported in the sky throughout history, UFOs became culturally prominent after World War II, escalating during the Space Age. Studies and investigations into UFO reports conducted by governments (such as Project Blue Book in the United States and Project Condign in the United Kingdom), as well as by organizations and individuals have occurred over the years without confirmation of the fantastical claims of small but vocal groups of ufologists who favour unconventional or pseudoscientific hypotheses, often claiming that UFOs are evidence of extraterrestrial intelligence, technologically advanced cryptids, demons, interdimensional contact or future time travelers. After decades of promotion of such ideas by believers and in popular media, the kind of evidence required to solidly support such claims has not been forthcoming. Scientists and skeptic organizations such as the Committee for Skeptical Inquiry have provided prosaic explanations for UFOs, namely that they are caused by natural phenomena, human technology, delusions, and hoaxes. Beliefs surrounding UFOs have inspired parts of new religions even as social scientists have identified the ongoing interest and storytelling surrounding UFOs as a modern example of folklore and mythology understandable with psychosocial explanations.
Benjamin Radford has pointed out how unlikely such suppression of evidence is given that "[t]he UFO coverup conspiracy would have to span decades, cross international borders, and transcend political administrations" and that "all of the world's governments, in perpetuity, regardless of which political party is in power and even among enemies, [would] have colluded to continue the coverup."
Notable proponents
A wide variety of people have publicly promoted the idea of a conspiracy to cover up UFOs.
A number of theorists achieved prominence for their claims. Donald Keyhoe was the most prominent proponent of UFO conspiracy theories during the 1950s. In the late 1960s and 1970s, Jacques Vallée and J. Allen Hynek were notable voices alleging a "Cosmic Watergate"; both were involved in the blockbuster Close Encounters of the Third Kind. In the 1980s, Stanton Friedman rose to prominence after describing the Roswell incident as a conspiracy. In the 2010s, Luis Elizondo rose to prominence for his claims of a US government cover-up.
Other proponents were less prominent. Richard Shaver, one early proponent, had been hospitalized for psychiatric problems, and Edgar Mitchell. and Israeli brigadier general Haim Eshed (former director of space programs for the Israel Ministry of Defense), In 2017, To The Stars Inc. was founded by Jim Semivan, Harold E. Puthoff, and Tom DeLonge. Luis Elizondo and David Grusch were notable proponents in the 2020s. Beyond their testimonies and reports they have presented no evidence to substantiate their statements and claims.
Theoretical physicist, Avi Loeb, claimed that interstellar objects, such as comets 1I/ʻOumuamua and 3I/ATLAS, and the meteor CNEOS 2014-01-08, are remnants of alien spacecraft. Some of Loeb's claims have been described as conspiracy theories, with USA Today referring to Loeb's speculation about 3I/ATLAS as an "outlandish conspiracy theor[y]."
In popular fiction
Works of popular fiction have included premises and scenes in which a government intentionally prevents disclosure to its populace of the discovery of extraterrestrial intelligence.
The 1960s saw conspiracy films like 2001: A Space Odyssey (as well as the novel),. The 1970s saw the UFO conspiracy discussed briefly in Jack Nicholson vehicle Easy Rider, and in-depth in the Steven Spielberg films Close Encounters of the Third Kind. The 1980s saw Spielberg return to the topic with E.T. the Extra-Terrestrial while Disney's Flight of the Navigator introduced UFO conspiracy theories to a childhood audience. The 1990s saw UFO conspiracy theories in films like Total Recall, Independence Day, and Men in Black.
The plot of the Sidney Sheldon novel The Doomsday Conspiracy involves a UFO conspiracy, as did the plot of the 2021 series American Horror Story: Double Feature.
In religion
Scholars of religion have identified some new religious movements among the proponents of UFO conspiracy theories, most notably the Nation of Islam, Scientology, and Heaven's Gate.
Mormon cosmology teaches that the Earth is not unique, but that it is one of many inhabited planets, with each planet created for the purpose of bringing about the "immortality and eternal life" (i.e., the exaltation) of humanity.
One author observes "there has long been an association between UFOs and The Church of Jesus Christ of Latter-day Saints".
Theosophists and occultists had long claimed knowledge of extraterrestrial beings. In 1946, Meade Layne achieved national notoriety when the wire service carried his claims to be in telepathic communication with people in a space ship.
Kenneth Arnold ignites flying disc craze
thumb|right|Army officials pose with balloon debris from Roswell.
The flying disc craze began on June 24, when media nationwide reported civilian pilot Kenneth Arnold's story of witnessing disc-shaped objects which headline writers dubbed "Flying Saucers". Such reports quickly spread throughout the United States; historians would later chronicle at least 800 "copycat" reports in subsequent weeks, while other sources estimate the reports may have numbered in the thousands. The Roswell incident did not surface again until 1978, when ufologist Stanton Friedman interviewed Jesse Marcel.
In late July, Palmer contacted Kenneth Arnold and asked him to investigate a "flying disc" report from Fred Crisman near Maury Island, Washington.
Wrote Shaver:<blockquote> "The discs can be a space invasion, a secret new army plane — or a scouting trip by an enemy country...OR, they can be Shaver's space ships, taking off and landing regularly on earth for centuries past, and seen today as they have always been — as a mystery. They could be leaving earth with cargos of wonder-mech that to us would mean emancipation from a great many of our worst troubles— and we'll never see those cargos...I predict that nothing more will be seen, and the truth of what the strange disc ships really are will never be disclosed to the common people. We just don't count to the people who do know about such things. It isn't necessary to tell us anything."
The article examined the Mantell UFO incident and quoted an unnamed pilot who opined that the Air Force's explanation "looks like a cover up to me". The article claimed a "rocket authority at Wright field" had concluded saucers were interplanetary. Concern over a public panic, of the kind that supposedly occurred after the 1938 War of the Worlds broadcast, is cited in the article as a possible motive for the cover up.
The True article caused a sensation.
thumb|UFO conspiracy proponent Donald Keyhoe (right) interviewed by Mike Wallace on March 8, 1958 Keyhoe claims the existence of a "silence group" orchestrating this conspiracy.
The first "alien bodies" conspiracy theory emerged in October and November 1949, when journalist Frank Scully published two columns in Variety. His 1950 book Behind the Flying Saucers expanded on the theme, adding that there had been two such incidents in Arizona and one in New Mexico, a 1948 incident that involved a saucer that was nearly in diameter. In January 1950, Time Magazine skeptically repeated stories of crashed saucers with humanoid occupants.
It was later revealed that Scully had been the victim of "two veteran confidence artists".
In 1952 and 1956, True magazine published articles by San Francisco Chronicle reporter John Philip Cahn that exposed Newton and "Dr. Gee" (identified as Leo A. GeBauer) as oil con artists who had hoaxed Scully.
In a 1997 Roswell report, Air Force investigator James McAndrew wrote that "even with the exposure of this obvious fraud, the Aztec story is still revered by UFO theorists. Elements of this story occasionally reemerge and are thought to be the catalyst for other crashed flying saucer stories, including the Roswell Incident."
Air Force accounts
thumb|right|General Samford press conference on flying saucers
On July 29, 1952, General John Samford, the director of Air Force intelligence, held a press conference on the recent UFO sightings over the nation's capital. The conference was the largest one held in the seven years since World War II.
Al Chop, a civilian, had served as the Press Chief for Air Materiel Command in Dayton, Ohio until 1951 when he transferred to the Pentagon to serve as the press spokesman for Project Bluebook. In 1956, a film titled Unidentified Flying Objects: The True Story of Flying Saucers dramatized the events of the early 1950s from the point of view of "Al Chop", an Air Force press officer played by reporter Tom Towers. The film incorporates interviews with actual eyewitnesses and historic footage of unidentified objects, concluding with a dramatization of the 1952 UFO flap that featured repeated sightings over Washington D.C.
In January 1956, Jessup began receiving a series of letters from "Carlos Miguel Allende", later identified as Carl Meredith Allen. "Allende" warned Jessup not to investigate the levitation of UFOs and spun a tale of a dangerous experiment in which a navy ship was made invisible, only to inexplicably teleport from Philadelphia to Norfolk, Virginia, before reappearing back in Philadelphia.
Jessup died by suicide in 1959. By 1975, the Philadelphia Experiment was being promoted by paranormal author Charles Berlitz and in 1984, the legend was adapted into a fictional film. In 1980, Berlitz co-authored The Roswell Incident.
1960–70s: Growing distrust in government
The 1960s began an era of government skepticism. After the assassination of John F. Kennedy, the Pentagon Papers, and the Watergate scandal, trust in the US government declined and acceptance of conspiracy theories became widespread.
Despite the near-universal condemnation of the prosecution, conspiracy theories continued to link Crisman to the Kennedy assassination and a supposed UFO cover-up. Crisman had been involved in the Shaver Mystery and the Maury Island Hoax in the 1940s. In the late 1970s, the United States House Select Committee on Assassinations considered the possibility that Crisman may have been one of the "three tramps" detained and photographed in the aftermath of the JFK assassination. The film was prominent in Moon landing conspiracy theories, which variously argue that humans never went to the Moon, went there with the assistance of aliens, or even that NASA covered up lunar evidence of aliens. One scholar opined that the 1968 film "seems to anticipate the post-Nixonian culture of governmental conspiracy".
J. Allen Hynek was an American astronomer who served as scientific advisor to UFO studies undertaken by the U.S. Air Force. Hynek had drawn ridicule for his most famous debunking, in which he suggested a mass-sighting over Michigan may have been caused by "swamp gas". By 1974, the former skeptic was publicly charging that Bluebook was "a Cosmic Watergate". In 1976, pulp publisher Ray Palmer argued "there is a definite link between flying saucers, The Shaver Mystery, The Kennedy’s assassinations, Watergate and Fred Crisman." expanded in the 1966 book Incident at Exeter, and became the basis for a 1968 science-fiction novel The Fortec Conspiracy. Fortec was about a fictional cover-up by the Air Force unit charged with reverse-engineering other nations' technical advancements. The Air Force explained that no "Hangar 18" existed at the base, noting a similarity between Carr's story and the fictional Fortec Conspiracy. In the mid-1970s, author Leonard H. Stringfield promoted tales of UFO crash retrievals. The 1980 film Hangar 18, which dramatized Carr's claims, was described as "a modern-day dramatization" of Roswell by the film's director James L. Conway, and as "nascent Roswell mythology" by folklorist Thomas Bullard.
"Alien Abductions"
In 1975, millions of Americans watched when NBC aired film The UFO Incident, a dramatization of the Betty and Barney Hill case, the first reported "alien abduction". Psychologists and skeptics argued that "after viewing this movie, any person with a little imagination could now become an instant celebrity" by claiming an abduction, concluding that "one of those instant celebrities was Travis Walton." Science writers Philip J. Klass and Michael Shermer highlight a potential motive for the hoax was to provide an "Act of God" that would allow the crew to avoid a steep financial penalty from the Forestry Service for failing to complete their contract by the deadline.
By 1976, artist and amateur UFO researcher Budd Hopkins began focusing on abduction reports; Hopkins popularized the reports in his 1981 book Missing Time and its 1987 follow-up Intruders. In 1989, the book was adapted into a film of the same name, starring Christopher Walken.
Close Encounters of the Third Kind
thumb|right|J. Allen Hynek (left) and Jacques Vallée were both involved in Close Encounters of the Third Kind
In 1974, the film UFOs: Past, Present, and Future dramatized an ostensibly-historical meeting between humans and aliens who land after being summoned. The depiction of a landing in the blockbuster Close Encounters of the Third Kind has been called a "thinly veiled reference to the Holloman landing" story. The Holloman story would be later promoted by hoaxer Richard Doty. The film's subplot of an "exchange program" of humans visiting aliens would later resurface in conspiracy theory as Project Serpo. Marcel revealed that the 1947 "weather balloon" had been a cover story, saying: "They wanted some comments from me, but I wasn't at liberty to do that. So, all I could do is keep my mouth shut. And General Ramey is the one who discussed – told the newspapers, I mean the newsman, what it was, and to forget about it. It is nothing more than a weather observation balloon. Of course, we both knew differently."
Uncertain of the material's origin, Marcel would speculate the debris might have been extraterrestrial. In all his statements, Marcel consistently denied the presence of bodies. On February 28, 1980, sensationalist tabloid the National Enquirer brought large-scale attention to the Roswell story.
In the 1990s, the US military published two reports disclosing the true nature of the crashed aircraft: a surveillance balloon from Project Mogul. Nevertheless, the Roswell incident continues to be of interest to the media, and conspiracy theories surrounding the event persist. Roswell has been described as "the world's most famous, most exhaustively investigated and most thoroughly debunked UFO claim".
Doty and Lear promote the "Dark Side"
In the 1980s, UFO conspiracy theories began to incorporate politics, alleging that the US Government was in league with an evil alien race. By way of contrast with prior UFO conspiracy theories about benevolent 'space brothers', author Jerome Clark named this new strain of thinking "ufology's dark side".
Writing in 2010, Pilkington reflects: "The silent helicopter has now been revealed as not only a reality, but one that was flying as long ago as 1972. This was the Hughes 500P, the P standing for Penetrator, an aircraft known by the few who flew it as ‘The Quiet One’."
150px|thumb|right|Linda Moulton Howe in 1981
In 1979, Linda Moulton Howe was a documentarian exploring cattle mutilations.