An Unidentified flying object (also called flying saucer and often abbreviated to UFO) is an anomalous phenomenon observed to me moving above ground level. In rare cases the object may be on the ground, or may be seen in the sea. A UFO is on rare occasions seen to be occupied by unidentified beings, some of whom may have communicated with humans.
- 1947: in Roswell, New Mexico, an object crashes into the ground. Subsequent operations to remove the debris, and the secrecy surrounding it, eventually lead to the case become world famous.
- 1947: pilot Kenneth Arnold sees several large, shining objects flying in formation in Washington State, USA. His use of the word "saucer" to describe them leads to the term "flying saucer" becoming popular.
- 1950: Antonio Villas Boas, a Brazilian farmer, reports boarding a UFO and having sex with a female occupant.
- 1952: A large number of UFOs fly en masse over Washington D.C.
- 1961: Betty and Barney Hill report being taken aboard a UFO in New Hampshire, USA.
- 1964: In Socorro, New Mexico, policeman Lonnie Zamora reports seeing two small beings board a small craft, which fies away, leaving marks on the ground.
- 1965: In Valensole, France, Lavender farmer Maurice Masse sees two small beings next to a round, metallic object in one of his fields. One of the beings stuns him from a few metres with a hand-held weapon. Later, a burnt patch of ground is found at the scene.
- 1973: in Pascagoula, Mississippi, two fisherman report being abducted by bizarre creatures and held captive on a UFO.
- 1980: In Texas, several witnesses observe a large UFO accompanied by military helicopters. Some of the witnesses suffer burns when the object flies too close to them.
- 1990: Belgium: many reports across the country of large Black triangles flying over urban areas at night.
Several theories have been put forward to explain (or explain away) UFOs. The most well known is the Extra-terrestrial hypothesis, which holds that the objects and their occupants come from outer space. Despite various criticisms of this idea, is it so well-established that the hypothesis is almost a given when UFOs are discussed, especially outside the specialist literature.