The United States

The Arnold sighting on 24 June 1947 did not arrive in a vacuum. The previous summer Sweden had logged a year-long wave of "ghost rockets" that triggered classified American intelligence assessments. Project Sign opened at Wright-Patterson Air Force Base in January 1948 with a remit to evaluate whether American skies were being penetrated by Soviet, captured Nazi, or otherwise unknown aircraft. Within eighteen months Sign's Estimate of the Situation reportedly concluded that the objects were interplanetary in origin. The Air Force chief of staff General Hoyt Vandenberg ordered the document burned. Project Sign was reorganised as Project Grudge in February 1949 with the prevailing direction reversed.

Roswell, New Mexico, in early July 1947 produced the most contested incident of the founding decade. Mac Brazel found debris on the Foster Ranch. Major Marcel collected it. The Roswell Army Air Field issued a press release on 8 July announcing the recovery of a flying disc. Within hours the story was retracted in favour of a weather balloon explanation. Marcel, his colleagues, and dozens of named witnesses spent the rest of their lives describing material and a recovery operation that did not match the official account. The archive holds the full Roswell exhibition, the contemporary press, and the Berlitz-Moore investigative work that surfaced the witness testimony in 1980.

By the summer of 1952 the United States had logged hundreds of military and civilian sightings annually. On the evenings of 19 and 26 July 1952, radar operators at Washington National Airport and Andrews Air Force Base tracked multiple unknowns moving over restricted airspace above the capital. F-94 interceptors were scrambled. Major General John Samford convened the largest Air Force press conference since the Second World War. The CIA assembled the Robertson Panel in January 1953 to consider whether the phenomenon constituted a national-security problem. The panel's recommendation, declassified in 1975, was that civilian interest should be discouraged.

Project Sign (1948), Project Grudge (1949), and Project Blue Book (1952 to 1969) ran the official United States Air Force investigation. Blue Book closed in December 1969 following the Condon Committee report at the University of Colorado, which recommended against further study. Twelve thousand six hundred cases passed through Blue Book's files. Seven hundred remained classified as unidentified at the time of closure. The archive holds the full Blue Book microfilm release through the National Archives, browsable through the document viewer at the United States Reading Room.

The civilian-research tradition outlived the official programmes by half a century. The Aerial Phenomena Research Organization in Tucson (1952 to 1988), the National Investigations Committee on Aerial Phenomena in Washington (1956 to 1980), the Mutual UFO Network in Texas (1969 to present), and the Center for UFO Studies in Illinois (1973 to present) accumulated case files that the Air Force was not collecting. The archive holds 258 issues of the APRO Bulletin, the MUFON UFO Journal, NICAP's UFO Investigator, and CUFOS publications, with deep-read article extraction across the four collections.

The classified-programme record returned to the public sphere in 2017. The 16 December 2017 New York Times article by Helene Cooper, Ralph Blumenthal, and Leslie Kean disclosed the existence of the Advanced Aerospace Threat Identification Program, AATIP, which had been funded inside the Defense Intelligence Agency between 2007 and 2012 by senate appropriation written by Harry Reid. The article was published alongside three Navy gun-camera videos. The Department of Defense subsequently confirmed those videos as authentic and stood up successor offices under different acronyms: the Unidentified Aerial Phenomena Task Force in 2020, the All-domain Anomaly Resolution Office (AARO) in 2022.

On 26 July 2023, three Navy aviators and one former intelligence officer testified under oath at a House Oversight subcommittee. David Grusch, a former senior officer at the National Reconnaissance Office and the National Geospatial-Intelligence Agency, alleged the existence of a multi-decade non-human craft retrieval and reverse-engineering programme. Ryan Graves and David Fravor described their own military encounters. The hearing was the first congressional testimony on UAP under oath since the 1968 Roush symposium. Two further House hearings followed in 2024 and 2025. The Schumer-Rounds UAP Disclosure Act, introduced in 2023 and re-introduced across three legislative cycles, has not yet passed in its original form.

Coral and Jim Lorenzen founded the Aerial Phenomena Research Organization out of their house in Sturgeon Bay, Wisconsin, in January 1952. APRO predated NICAP by four years and MUFON by seventeen. Its 36-year archive contains the earliest civilian field investigation of Roswell, the founding-period documentation of the Brazilian flap of 1957 to 1958, the Antonio Villas-Boas abduction, and the Walton case in November 1975. APRO's Tucson headquarters maintained the only American civilian network with active investigators in Latin America. The APRO Bulletin collection holds 258 issues, with 207 deep-read and 1,671 sighting reports extracted to the archive.

Donald Keyhoe assumed the directorship of the National Investigations Committee on Aerial Phenomena in 1957. Under his leadership NICAP cultivated military and intelligence contacts in Washington, lobbied Congress for an open hearing on UFOs, and published The UFO Investigator monthly through 1980. The 1968 congressional symposium under Representative J. Edward Roush emerged from Keyhoe's twelve-year campaign. The NICAP Investigator collection in the archive documents the Washington lobbying tradition in real time.

The Mutual UFO Network was founded in Quincy, Illinois, in 1969 by Walter Andrus, John Schuessler, and Allen Utke. MUFON's case-management system continues to log new American sighting reports. The MUFON UFO Journal, the organisation's monthly publication, ran from 1967 (originally as Skylook) to the present. The MUFON Journal collection covers the entire arc. The Center for UFO Studies was founded in Northfield, Illinois, in 1973 by J. Allen Hynek, the Northwestern University astronomer who had served as the Air Force's chief astronomical consultant on Projects Sign, Grudge, and Blue Book. CUFOS represents the academic-investigation tradition. The International UFO Reporter documents Hynek's late-career civilian work.

The 16 December 2017 New York Times article opened a cycle the United States Senate, the House of Representatives, the Department of Defense, the Office of the Director of National Intelligence, and NASA have all subsequently been drawn into. The Pentagon confirmed the FLIR1 video. The Department of the Navy revised its UAP reporting procedures in 2019. The Office of the Director of National Intelligence issued the June 2021 preliminary assessment acknowledging 144 military UAP incidents between 2004 and 2021. The All-domain Anomaly Resolution Office stood up in July 2022 under Sean Kirkpatrick, replaced by Jon Kosloski in December 2023. NASA convened its UAP independent study team in 2022 and published the findings in September 2023.

Congress acted in parallel. The 2023 National Defense Authorization Act contained the Gillibrand-Rubio UAP Disclosure provision requiring federal agencies to report UAP records to AARO. The Schumer-Rounds UAP Disclosure Act was introduced in 2023 with provisions for eminent domain over recovered non-human technology and a presidential review board modelled on the JFK Records Act. The Disclosure Act has been re-introduced three times. The four House Oversight hearings (2022, 2023, 2024, 2025) have placed witnesses including David Grusch, Ryan Graves, David Fravor, Lue Elizondo, Tim Phillips, Jon Kosloski and Sean Kirkpatrick under oath in the public record.

The journalism around this cycle has been led from Australia (Ross Coulthart at News Nation), the United States (Leslie Kean, Ralph Blumenthal, George Knapp, Bryce Zabel), and the United Kingdom (Nick Pope, Christopher Sharp at Liberation Times). The archive maintains the Disclosure Network as a parallel hub to the historical biographies, documenting the figures presently active in the post-2017 record.

The United States holds 87,990 sightings in the archive's sighting database, more than half of the global total. The first dated American sighting on file is from 1639, recorded by John Winthrop in the Massachusetts Bay Colony. The earliest of the 1890s wave is dated 1880. Modern-era reporting begins in 1947. The decade with the largest American sighting volume on record is the 2000s with 23,459 entries, followed by the 2010s, the 1990s, the 1950s and the 1970s. The most common reported shapes are Light (11,819 reports), Disc (6,586), Triangle (5,604) and Circle (4,182).

The shape and decade catalogue, the source breakdown, the most-frequently-reported counties, and the linked encyclopedia entries are all browsable from the Countries hub.