This is fascinating:
D. B. Cooper, aka “Dan Cooper”, is a pseudonym given to a notorious aircraft hijacker who on November 24, 1971, after receiving a ransom payout of $200,000, leapt from the back of a Boeing 727 as it was flying over the Pacific Northwest. No conclusive evidence has ever surfaced regarding Cooper’s whereabouts, and several theories offer competing explanations of what happened after his famed jump. The only clues to have turned up in the case are ambiguous: around $6,000 that washed up on the banks of the Columbia River, and part of a sign believed to be from the rear stairway of the plane from which Cooper jumped. The Cooper case remains the world’s only unsolved hijacking.