Frederick Valentich was a young pilot with about 150 hours of flight experience. He had applied to join the Royal Australian Air Force but been rejected twice. On October 21, 1978, he filed a flight plan for a solo night training flight from Moorabbin to King Island - a 125-mile route across Bass Strait.

The purpose of the flight was reportedly to pick up crayfish for sale to friends. Valentich had not booked ahead to collect any cargo. His father later said Frederick had been interested in UFOs and had reported seeing them before. The flight, from the beginning, had elements that didn't quite fit.

At 7:06 PM, while flying over Bass Strait, Valentich contacted Melbourne air traffic control. 'Is there any known traffic below five thousand?' The controller responded that there was no known traffic. Valentich reported that he could see a large unknown aircraft with four bright lights, passing above him about 1,000 feet.

Over the next six minutes, Valentich described the object repeatedly. It orbited above him. It approached at high speed. It had a green light and a shiny metal surface. When the controller asked him to identify the aircraft type, Valentich replied: 'It isn't an aircraft.'

At 7:12 PM, Valentich reported that his engine was rough-idling and that the object was 'just hovering' above him. Asked to identify the unknown aircraft, he responded: 'Delta Sierra Juliet, Melbourne, it is... [a] long pause [of about five seconds]... [the microphone remains open for about 17 seconds, with various metallic sounds]...'

Then silence. All attempts to re-establish contact failed. A search operation was launched immediately. Aircraft and boats scoured Bass Strait for days. No wreckage, no oil slick, no body was ever found. Frederick Valentich had vanished.

The official investigation could reach no conclusion. Theories ranged from pilot disorientation and suicide to staging his own disappearance. Some UFO researchers claimed Valentich had been abducted. Others suggested he had encountered some unusual atmospheric phenomenon.

The metallic sounds at the end of the recording have never been identified. They were analyzed by audio experts but matched no known aircraft sounds. Five years after the disappearance, an engine cowl flap that might have been from a Cessna 182 washed up on Flinders Island. It was never definitively linked to Valentich's aircraft.

The Valentich disappearance remains officially unexplained. Multiple UFO sightings were reported in the area that evening, though none were ever verified. The Australian Department of Transport's final report concluded only that the pilot could not be found and the reason for his disappearance was unknown.

The case became famous worldwide as one of the best-documented aviation disappearances possibly involving a UFO. The audio recording of Valentich's final transmissions has been studied, enhanced, and debated for decades. What happened over Bass Strait on October 21, 1978? A young pilot vanished while describing something he couldn't identify. Beyond that, no one knows.