In 1971, a man calling himself Dan Cooper boarded a flight out of Portland, handed a note to a flight attendant, and calmly claimed he had a bomb. What followed became one of the most famous hijackings in American history — a ransom drop, a midnight parachute jump into rough wilderness, and a suspect who vanished without a trace.

Over the next five decades, theories multiplied, evidence surfaced and disappeared, and a mysterious bundle of cash washed up along the Columbia River. Despite one of the longest and most exhaustive investigations the FBI ever launched, the true identity — and fate — of D.B. Cooper remains one of the country’s most enduring unsolved mysteries.