#6 D.B. Cooper
On the 24th of November 1971, a man called D.B. Cooper hijacked a Boeing 727 to Seattle. After extorting $200,000 in ransom, the man grabbed a parachute and jumped out of the plane.
What’s surprising is that the pilots of the five planes that were trailing the hijacked plane never saw him jump and therefore, couldn’t locate where he could have landed. This case was officially suspended in July 2016, but still open for speculations.