On 21 October 1978, Frederick Valentich, a 20-year-old pilot with about 150 hours, was flying a Cessna 182 from Melbourne to King Island across Bass Strait. He radioed Melbourne Flight Service to report an aircraft above him. The exchange lasted roughly six minutes, ended with an unidentified metallic sound, and neither Valentich nor the Cessna was ever found.
What the transcript records
The official transcript is a matter of record, and it is unusual reading. Valentich reports a large aircraft above him with four bright landing lights. He asks the controller to identify traffic; the controller reports no known traffic in the area. He describes the object passing over him at speed, then says it is orbiting above him and that it is "not an aircraft".
His final transmission reports engine trouble — rough running — and then the recording captures seventeen seconds of an unidentified metallic scraping sound before the transmission ends.
What the investigation found
The Australian Department of Transport investigation concluded the cause could not be determined and that the aircraft was presumed lost. It was unable to establish what Valentich saw.
An oil slick was reported in the strait, but analysis did not link it to the aircraft. A search covering a large area of water found nothing. A part later recovered from a beach was examined and could not be conclusively tied to the aircraft.
The conventional explanations
Spatial disorientation. A low-hour pilot flying at dusk over water with no visible horizon is in classic conditions for disorientation. If he had entered an unrecognised bank, he could have been flying in a slow spiral. The lights he described could have been his own aircraft's reflections, or celestial objects. In an inverted or steeply banked attitude, an object that appeared to be "above" him could have been on the sea surface below.
This explanation covers a surprising amount of the transcript, including the reported engine trouble — a fuel-starved engine in an unusual attitude behaves exactly as described.
Astronomical objects. Analysis of the sky that evening has been used to argue that bright planets and stars in that direction could account for the reported lights, given the conditions.
Other accounts. Various claims about the flight's purpose or the pilot's intentions have circulated. None has been substantiated.
Why it endures
The Valentich case survives because the source material is unusually good. There is an official transcript of a pilot describing something in real time to a controller, and there is a recorded sound at the end that has never been explained. That combination is rare, and it means the case cannot simply be dismissed as anecdote.
It also cannot be resolved. Without the aircraft, there is no way to distinguish between a disoriented pilot describing what disorientation feels like, and anything else.