DB Cooper Vane

On November 24, 1971 a man using the alias Dan Cooper purchased an airline ticket at Portland, Oregon and later while enroute to Seattle, Washington (NWA Flight 305) proceeded to hijack the Boeing 727-100 that he was traveling on.
D. B. Cooper, as the man is better known, claimed to have a bomb and demanded $200,000 in unmarked $20 bills, four parachutes (two primary and two reserve), and a fuel truck standing by in Seattle to refuel the aircraft upon arrival.
After circling the Puget Sound for approximately two hours to allow Seattle police and the FBI time to assemble everything that Cooper demanded, Flight 305 landed at the Seattle-Tacoma Airport at 5:39 pm.
During refueling Cooper outlined his flight plan to the cockpit crew; he instructed them to fly at an airspeed of approximately 100 kts, no higher than 10,000 feet, landing gear down, unpressurized, and with flaps extended to 15°. (Under these conditions they also decided to land and refuel at Reno, Nevada.)
Finally after the refueling was complete and the money and parachutes had been delivered, Cooper released his hostages and at approximately 7:40 pm the 727 took off headed towards Reno, NV. Within 20 minutes the flight crew noticed that the airstair had been extended and by 8:13 pm Cooper had jumped out of the aircraft (some believe in the Washougal River Valley in the state of Washington).

15 hijackings similar to D.B. Cooper’s were attempted later in 1972 (at least 4 successful parachute landings recorded) but all hijackers were captured. It was evident that something had to be done to prevent future hijackings of aircraft equipped with airstair doors so in early 1972 the FAA mandated that all Boeing 727 aircraft be fitted with a device, later dubbed the “Cooper vane”, which prevented lowering of the aft airstair during flight. (Beginning in 1973 the FAA also required airlines to search all passengers and their bags.)

On the ground In Flight

The Cooper vane is a very simple paddle type device which is spring loaded in such a way that while on the ground it allows the aft airstair door to be opened. When the aircraft is in the air the airflow over the paddle causes it to rotate 90° so that the plate that the paddle is attached to blocks the airstair door from opening. Once the airflow decreases on landing, the spring-loaded paddle returns to its initial position, thereby allowing the stairs to be lowered again.

Despite an extensive manhunt and an ongoing FBI investigation, D.B. Cooper has never been located or positively identified. The case remains the only unsolved air piracy in American aviation history.