Frederick Valentich (/ˈvæləntɪtʃ/) was an Australian pilot who disappeared while on a 125-nautical-mile (232 km) training flight in a Cessna 182L light aircraft, registered VH-DSJ,[1] over Bass Strait.

[1] Five years after Valentich's aircraft went missing, an engine cowl flap was found washed ashore on Flinders Island.

In July 1983, the Bureau of Air Safety Investigation asked the Royal Australian Navy Research Laboratory (RANRL) about the likelihood that the cowl flap might have "travelled" to its ultimate position from the region where the aircraft disappeared.

[10] According to Brian Dunning, Valentich's radio conversation was similar to the dialogue from a scene in the film Close Encounters of the Third Kind, which was released less than a year before the disappearance, and was popular among pilots, young people and UFO fans.

Dunning speculated that it is possible that Valentich was trying to imitate the scene for fun, and deliberately made his aircraft fly in a circular pattern in order to "give the radar guys something to see", but accidentally became disorientated and crashed into the water.

[11] A 2013 review of the radio transcripts and other data by astronomer and retired United States Air Force pilot James McGaha and author Joe Nickell proposes that the inexperienced Valentich was deceived by the illusion of a tilted horizon for which he attempted to compensate and inadvertently put his aircraft into a downward, so-called "graveyard spiral" which he initially mistook for simple orbiting of the aircraft.

According to the authors, the G-forces of a tightening spiral would decrease fuel flow, resulting in the "rough idling" reported by Valentich.

[1] Ufologists have claimed that a UFO either destroyed Valentich's aircraft or abducted him, saying that some individuals reported seeing "an erratically moving green light in the sky" and that he was "in a steep dive at the time".

[3] The group Ground Saucer Watch, based in Phoenix, Arizona, United States, claims that photos taken by plumber Roy Manifold on the day of Valentich's disappearance show a fast-moving object exiting the water near Cape Otway Lighthouse.