"IT'S NOT AN AIRCRAFT" — the Valentich tapes, and the boring explanation I keep coming back to

This gets posted as alien abduction every single time so let me play the annoying skeptic, then admit where it still gets me. Oct 21 1978, Frederick Valentich, 20, low-hours pilot, rents a Cessna 182 to fly over Bass Strait from Moorabbin to King Island, Australia. Evening, calm. He radios Melbourn……