Background
On 24 November 1971 an unknown man calling himself Dan Cooper hijacked Northwest Orient Flight 305 between Portland and Seattle, claiming to have a bomb. He demanded $200,000 and four parachutes, released the passengers in Seattle and, after take-off, jumped from the aircraft with the ransom over a wooded area of south-western Washington State. His identity and fate have never been established; in 1980 a small part of the money was found on the banks of the Columbia River. The case, known as 'D. B. Cooper' because of a reporter's error, led to stricter airport security.
Sources: FBI: D. B. Cooper Hijacking (Famous Cases) · Wikipedia: D. B. Cooper