Roswell incident

Debris found by a rancher in 1947 near Roswell, New Mexico, has become the basis for UFO conspiracy theories alleging that the United States military recovered a crashed extraterrestrial spacecraft. After metallic and rubber debris was recovered by Roswell Army Air Field personnel, the United States Army Air Forces announced possession of a "flying disc". This announcement made international headlines, but was retracted within a day. The debris was from a complex and uncrewed military balloon train consisting of linked balloons and assorted equipment, operated from the nearby Alamogordo Army Air Field as part of the top-secret Project Mogul, a program intended to detect Soviet nuclear tests. To obscure the purpose and source of the debris, the army reported that it was merely a conventional weather balloon.

In 1978, retired United States Air Force officer Jesse Marcel revealed that the Army's weather balloon claim had been a cover story, and speculated that the debris was of extraterrestrial origin. Popularized by the 1980 book The Roswell Incident, this speculation became the basis for long-lasting and increasingly complex and contradictory conspiracy theories, which over time expanded the incident to include governments concealing evidence of extraterrestrial beings, grey aliens, multiple crashed flying saucers, alien corpses and autopsies, and the reverse engineering of extraterrestrial technology, none of which have any factual basis.