USAAC/ USAAF/ USAF aircraft designation systems

The US Air Force and its predecessors have used a series of designation systems to identify their aircraft, starting by using the manufacturer's own codes then adopting a system of type numbers and two letter codes in 1919-20. This was replaced by the more familiar basic mission system in 1924, with single letters for most aircraft types. This remained in use (with variants) until 1962, when it became the basis of the current Tri-service aircraft designation system.