In September 1976, two Iranian F-4 Phantoms closed on a brilliant light over Tehran — and their instruments and weapons died on approach. A US intelligence file calls the report outstanding. Nothing calls it solved.

In 1986 a veteran 747 captain reported an object he said dwarfed his jumbo jet, pacing him for 400 miles across the Alaskan twilight. The FAA logged the crew statements, the radar and the voice tapes - and to this day cannot confirm a thing.

In November 2004, a US Navy cruiser tracked impossible radar returns for days. Then two fighter pilots saw the thing with their own eyes — and the official file remains open.

Over two nights in December 1980, American servicemen at a NATO base in England chased lights through the trees. Their deputy commander sent an official memo to the British government. It has never been explained.