Frederick Valentich 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, over Bass Strait.

On the evening of Saturday 21 October 1978, twenty-year-old Valentich informed Melbourne air traffic control that he was being accompanied by an aircraft about 1,000 feet (300 m) above him and that his engine had begun running roughly, before finally reporting: “It’s not an aircraft.”

Valentich radioed Melbourne Flight Service at 7:06 pm to report that an unidentified aircraft was following him at 4,500 feet (1,400 m). He was told there was no known traffic at that level. Valentich said he could see a large unknown aircraft which appeared to be illuminated by four bright landing lights. He was unable to confirm its type, but said it had passed about 1,000 feet (300 m) overhead and was moving at high speed. Valentich then reported that the aircraft was approaching him from the east and said the other pilot might be purposely toying with him. Valentich said the aircraft was “orbiting” above him and that it had a shiny metal surface and a green light on it. Valentich further reported that he was experiencing engine problems. Asked to identify the aircraft, Valentich radioed: “It’s not an aircraft.” His transmission was then interrupted by unidentified noise described as “metallic, scraping sounds” before all contact was lost.