The United States Air Force (USAF) is the aerial warfare service branch of the United States Armed Forces and one of the seven American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on 18 September 1947 under the National Security Act of 1947. It is the most recent branch of the U.S. military to be formed, and is the most technologically advanced air force in the world. The USAF articulates its core functions in its 2010 Posture Statement as Nuclear Deterrence Operations, Special Operations, Air Superiority, Global Integrated ISR, Space Superiority, Command and Control, Cyberspace Superiority, Personnel Recovery, Global Precision Attack, Building Partnerships, Rapid Global Mobility and Agile Combat Support.

As of 2009^[update] the USAF operates 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, 2,130 air-launched cruise missiles, and 450 intercontinental ballistic missiles. The USAF has 330,159 personnel on active duty, 68,872 in the Selected and Individual Ready Reserves, and 94,753 in the Air National Guard as of September 2008. In addition, the USAF employs 151,360 civilian personnel, and has over 60,000 auxiliary members in Civil Air Patrol, making it the largest air force in the world.