UFOs (Unidentified Flying Objects) are mysterious objects seen in the sky for which, it is claimed, no orthodox scientific explanation can be found and which are frequently speculated to be extraterrestrial spacecraft.
The acronym "UFO" was coined by Capt. Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs.
In real life, people frequently consider it plausible that UFOs are of extra-terrestrial origins.
The UFOs first appeared in Science Fiction as far back as 1930s Flash Gordon