D.B. Cooper

On November 24, 1971 an unidentified suspect hijacked a Boeing 727 en route from Portland to Seattle. The suspect, popularly known as D.B. Cooper, the alias under which he bought his ticket to Seattle, successfully extorted $200,000 and disappeared later that evening. You can read more about him here:
D.B. Cooper

Whoever Cooper was, he knew his airplanes. The 727 is designed with a set of airstairs at the aft end of the pressure cabin, allowing passengers and crew to enter and exit the airplane without a jetway or Bluth-family-surplus stair car. This is good for accessing remote airports and avoiding hop-ons. Cooper figured that what works on the ground might also work in the air at relatively low speed. After threatening to detonate a bomb if his demands for money and parachutes were not met, the flight crew circled Puget Sound for several hours as Seattle police and the FBI assembled Cooper's wish list. The airplane then landed at Sea-Tac Airport, where Cooper released the passengers, collected his ransom, and ordered the pilots to fly low and slow toward Mexico. After dark and over the thick evergreen forests of southern Washington, Cooper deployed the airstairs and left the airplane, never to be heard from again.

No one knows what happened to Cooper after his elegant exit, but the most likely explanation is that he didn't survive his jump. Even at "low" speed for a jetliner, the stairs would've been flailing under category 3 hurricane-force winds, and it's possible Cooper was incapacitated by moving aircraft structure on his way out. Once he departed the 727 Cooper descended in pitch darkness over an unpopulated mountainous area. Unless he pulled the ripcord immediately after exit, it's entirely possible that he impacted the ground without ever knowing it was right in front of him. Even if he successfully egressed and deployed his chute, the landing in dense pine forest without visual aid would've been necessarily rough, and he may have been too injured to move after landing in a thicket. Most tellingly, while every bill issued by the FBI to Cooper was photographed and microfilmed, the only ransom bills that have been recovered were found rotting on a bank of the Columbia River nine years later. It would be odd to go to all the trouble to hijack an airplane and extort the federal government only to disappear without spending any of the ransom.

This is all speculation. The fact is that nobody really knows what happened to Mr. Cooper, or who he was, or if he simply did this as a prank on the airlines and the governments of both Washingtons. Perhaps some day he'll come out of the woodwork to tell the story from his end. I'm not counting on it, but the truth is out there.