The UH-1 Huey helicopter was the iconic helicopter of the Vietnam War. The Bell UH-1 Iroquois, a utility military helicopter powered by a single turboshaft engine with two-blade main and tail rotors, was developed by Bell Helicopter to meet the Army's requirement for a medical evacuation and utility helicopter and first flew in 1956. It was the first turbine-powered helicopter in the US military, and more than 16,000 were built. The UH-1 Huey first saw combat operations during the Vietnam War, with 6994 deployed. Its two-bladed design produced the characteristic "Huey thump" sound in flight. Internal seating included 2 pilot seats and additional seating for 13 passengers or crew, and the cabin could be configured to hold six medical stretchers or equivalent cargo. It could be modified for many different missions, and in Vietnam its primary missions included general support, air assault, cargo transport, medical evacuation, search and rescue, electronic warfare, and ground attack. During the Vietnam War, 11,835 helicopters of all types from all branches of service served, including 6994 Hueys; of those total helicopters, 5607 were lost, 2165 helicopter pilots were killed in action, 2712 crewmembers were killed in action, and 40,000 helicopter pilots served in the war. The UH-1 Huey had a capacity of 3880 pounds, a length of 57'1" with rotors, a width of 8'7", a height of 14'5", a maximum takeoff weight of 9500 pounds, a main rotor diameter of 48 feet, a maximum speed of 135 mph, a range of 315 miles, and a flying ceiling of 19,390 feet.