The United States Air Force (USAF) is the aerial warfare branch of the armed forces and one of the seven uniformed services of the United States. Initially part of the United States Army as the Army Air Corps, the USAF was formed as a separate branch of the military on September 18, 1947. It was the last branch of the US military to be formed.
The USAF is one of the largest and most technologically advanced air forces in the world, with about 5,573 manned aircraft in service (3,990 USAF; 1,213 Air National Guard; and 370 Air Force Reserve); approximately 180 Unmanned Combat Air Vehicles, 2130 Air-Launched Cruise Missiles, and 450 Intercontinental Ballistic Missiles; and has 330,159 personnel on active duty, 68,872 in the Selected and Individual Ready Reserves, and 94,753 in the Air National Guard. In addition, the Air Force employs 151,360 civilian personnel.
The Department of the Air Force is headed by the civilian Secretary of the Air Force who heads administrative affairs. The Department of the Air Force is a division of the Department of Defense, headed by the Secretary of Defense. The highest ranking military officer in the Department of the Air Force is the Chief of Staff of the Air Force.