The prototype Bell Model 204 initially flew in 1956 and was the first turbine powered aircraft ordered by the U.S. Army. Designated the H-40 following the USAF designating system, this aircraft was re-designated the HU-1 when it entered service in 1959. Although officially named “Iroquois,” it was better known as the “Huey” based on this designation. In 1962, the U.S. Military changed it’s designating system and again changed the designation of the “Huey” to UH-1. At the same time a lengthened version, the Model 205 was introduced. This went into service as the UH-1D. This model had its first flight on August 16, 1961, and went on to become the popular “Huey” that saw extensive service in the Vietnam War. Capacity was up to 12 fully-equipped troops plus its crew of two. As an aerial ambulance, it could carry four litters and the attendant medical technicians.