Found this on planecrashinfo.com

On November 24, 1971, a man calling himself Dan Cooper boarded a Boeing 727, Northwest Airlines, Flight 305 at Portland Oregon bound for Seattle Washington. Soon after the plane took off , Cooper, seated in seat 18C, stated he had a bomb. He demanded $200,000 in cash and several parachutes. After the plane landed at Seattle, the passengers were allowed to leave. Cooper and four crew members took off with his instructions to fly towards Mexico. The pilot was instructed to fly no higher that 10,000 feet and below 200 mph. He asked the flight attendant how to open the tail stairway and ordered her to the front of the plane. Shortly after, the crew felt a thud and Cooper jumped from the plane with a 21 lb. package of money tied to his waist. He was never heard from again. Despite a massive search, no sign of him was ever found. The FBI calculated he landed somewhere near Ariel, Washington. Cooper jumped into the darkness at 7 below zero temperatures with strong winds and freezing rain. He was not equipped to survive in the wilderness. Cooper, who became somewhat of a folk-hero in succeeding years, was probably killed in the jump or succumbed to the elements. The day after the skyjacking, FBI agents checked out a Portland man with the name D.B. Cooper but quickly cleared him. The newspapers picked up on it and incorrectly call the hijacker D.B. Cooper which stuck and was never corrected. In 1980, a boy playing on the banks of the Colombia River found 5,800 dollars in 20 dollar bills buried in the sand which matched the serial number of the money given to Cooper. Cooper’s lasting contribution to aircraft design is the "Cooper Vane," a latching device on Boeing 727s that prevents the tail stairway from being lowered in flight.