co-found Horizon Airlines and Aviation Partners Inc. The Mark VI system included nacelle wing lockers, dual aft body strakes, exhaust stack fairings, engine inlet ram air recovery system, high-flotation landing gear doors and enhanced performance inboard wing leading edge. Raisbeck went on in 1983 to develop Quiet Turbofan Propellers for the King Air with Hartzell Propeller. The same propeller technology was later used by Raisbeck and Hartzell to develop a Quiet Turbofan Propeller for the de Havilland Canada DHC-6 Twin Otter. Installed on the King Air, the quiet propellers reduce the perceived noise levels enough to allow the airplanes to operate out of European airports with the most stringent noise requirements. In 1994 Raisbeck introduced the aft fuselage locker for Learjet 35/36 aircraft, which allows the carriage of up to 11 cubic feet (0.31 m3) and 300 lb (136 kg) of cargo with easy external access to the watertight locker. The locker was also later certified for use on the Learjet 31. Turning to airliners, in 1996 the Raisbeck Commercial Air Group completed recertification of the Boeing 727 to meet Stage 3 noise limits without weight and performance penalties. The Raisbeck Stage 3 Noise Reduction Systems for the Boeing 727 covered all models and weights. Aerodynamic innovation provided Stage 3 noise compliance without costly engine modifications, saving their operators several million dollars on each installation. American Airlines ordered and took delivery of 52 Raisbeck 727 Stage 3 systems. Other customers have included TWA, Pan Am, Air Algerie, TAME and many smaller airlines. In August 2001 Raisbeck delivered a redesigned overhead bin system for JetBlue's fleet of Airbus A320s. Because of the design of enlarged bins, popular, 22-inch, upright bags carried by passengers could be stored crosswise, with the handle facing the door. The redesigned overhead door and extended bin floor almost double the usable overhead storage space, allowing for quick and easy baggage stowage. Raisbeck has now equipped all of JetBlue's Airbus fleet of more than 100 aircraft. Raisbeck began developing bulletproof doors and bulkheads for Boeing 737s and 757s in 2000 (before the September 11-mandated FAA requirement). Four weeks after the September 11, 2001 attacks, the first of Raisbeck's prototype Hardened Cockpit Security System was installed. Alaska Airlines, American Trans Air and other airlines operating the Boeing 737 immediately ordered and took delivery of the cockpit doors. The doors included rapid decompression, emergency pilot egress and crash-crew cockpit ingress,