combat missions, in 1964 it adopted a modified version of the 269A as its training helicopter to replace the TH-23 and designated it the TH-55A Osage. 792 TH-55 helicopters would be delivered by 1969, and it would remain in service as the U.S. Army's primary helicopter trainer until it was replaced in 1988 by the UH-1 Huey. At the time of its replacement, over 60,000 U.S. Army pilots had trained on TH-55 making it the U.S. Army's longest serving training helicopter. In addition to the U.S. Army, Hughes delivered TH-55/269/300s to other military customers. In 1964, Hughes introduced the slightly larger three-seat Model 269B which it marketed as the Hughes 300. That same year, the Hughes 269 set an endurance record of 101 hours. To set the record, two pilots took turns piloting the aircraft and hovered in ground-effect for fueling. To ensure no cheating, eggs were attached to the bottom of the skid gear to register any record-ending landing. The Hughes 300 was followed in 1969 by the improved Hughes 300C (sometimes 269C), which first flew on 6 March 1969 and received FAA certification in May 1970. This new model introduced a more powerful 190 hp (140 kW) Lycoming HIO-360-D1A engine and an increased-diameter rotor, giving a payload increase of 45%, plus overall performance improvements. It was this model that Schweizer began building under license from Hughes in 1983. In 1986, Schweizer acquired all rights to the helicopter from McDonnell Douglas, who had purchased Hughes Helicopters in 1984, and renamed it McDonnell Douglas Helicopter Systems. For a few years after, Schweizer acquired the FAA Type Certificate known as the Schweizer-Hughes 300. While Schweizer made over 250 minor improvements, the basic design remained unchanged. Between Hughes and Schweizer, and including foreign-licensed production civil and military training aircraft, nearly 3,000 copies of the Model 269/300 have been built and flown over the last 50 years. That would have been the end of the story, but Schweizer continued to develop the model 300 by adding a turbine and redesigning the body to create the model 330m, and then further developed the dynamic components to take greater advantage of the power of the turbine engine; this led to the development of the Model 333. Variants Hughes 269 Two prototype aircraft powered by a 180 hp Lycoming O-360-A engine and had a truss tailboom. First flown on 2 October 1956. 269A Replacing the prototype's