Who is D.B. Cooper?

시즌 4, 에피소드 14: It's the only unsolved air piracy case in history. In 1971, a man hijacks a Northwest Orient Airlines flight, demanding 4 parachutes and $200,000. He jumps out of the plane with the money and is never seen again. Can new evidence finally reveal the identity of the anonymous hijacker known as D.B. Cooper?