The Valentich Disappearance occurred on 21 October 1978, when 20-year-old Frederick Valentich disappeared while piloting a small Cessna 182 aircraft over Bass Strait to King Island (Tasmania). Described as a "flying saucer enthusiast", Valentich informed Melbourne air traffic control he was being accompanied by an unknown aircraft.
So if you identify a UFO as a UFO, it becomes an FO, unless it has landed...then its just an O.