The Valentich disappearance describes an event on 21 October 1978 when 20-year-old Frederick Valentich disappeared in unknown circumstances while piloting a Cessna 182L light aircraft over Bass Strait, Australia. His intention was to land at King Island, pick up three or four friends there, and return to Moorabbin Airport.
During the 127 mile (235 km) private flight, Valentich advised Melbourne air traffic control he was being accompanied by an aircraft about 1,000 feet (300 m) above him. He described unusual actions and features of the aircraft, reported that his engine had begun running roughly, and finally reported before disappearing from radar that "That strange aircraft is hovering on top of me again. It is hovering and it's not an aircraft".
No trace of Valentich or his aircraft was ever found, and a Department of Transport investigation concluded that the reason for the disappearance could not be determined.
The report of a UFO sighting in Australia attracted significant press attention, in part due to the number of sightings reported by the public on that night.