The Air Force is the youngest military service. Prior to 1947, the Air Force was a separate Corps of the Army. The primary mission of the Army Air Corps was to support Army ground forces. However, World War II showed that air power had much more potential than simply supporting ground troops, so the Air Force was established as a separate service.

The primary mission of the Air Force is to defend the U.S. and its interests via air and space. It operates fighter aircraft, tanker aircraft, light and heavy bomber aircraft, transport aircraft, and helicopters. The Air Force is also responsible for all military satellites and controls strategic nuclear ballistic missiles. Like the Army, the active duty Air Force is supplemented by the Air Force Reserves and the Air National Guard.