FREDERICK.

At 7:06 p.m. he radioed Melbourne Flight Service Unit operator Steve Robey to ask whether there was any known traffic in his vicinity below 5,000 feet. Robey answered no. Over the next six minutes, Valentich described an unknown object passing him repeatedly at high speed, with four bright landing-light-style lights, "like a long shape … the thing is just orbiting on top of me also."

The recorded audio transcript, preserved by the Australian Department of Transport, captured Valentich's increasing distress. He reported that his engine was rough idling and coughing, that the object was directly above him, "it's not an aircraft," and finally a metallic scraping sound followed by a 17-second tone sometimes described as a metallic whirring. The transmission ended at 7:12 p.m. Despite an extensive sea and air search across Bass Strait, no trace of Valentich, the Cessna, or any wreckage has ever been found.

The Department of Transport investigation listed the cause of the loss as "unknown." A 1982 paper in the Journal of the Australian Maritime Safety Authority noted that an oil filter cap was discovered washed ashore at Flinders Island that may have come from a Cessna 182 of the appropriate year — but it could not be conclusively tied to Valentich's aircraft. Independent witnesses on the ground at Cape Otway and on King Island reported observing a green light pacing a smaller aircraft on that evening.

Speculative explanations have ranged from spatial disorientation, suicide, smuggling involvement, and a hoax to genuine encounter with an unknown craft. None has been substantiated. The Valentich disappearance remains the only documented case in modern aviation in which a pilot describing a UFO encounter in real time vanished mid-transmission. Australia's RAAF officially classifies the case as unexplained.