The United States Air Force (USAF) is the aerial and space warfare service branch of the United States Armed Forces. It is one of the five branches of the United States Armed Forces, and one of the seven American uniformed services. Initially formed as a part of the United States Army on 1 August 1907, the USAF was established as a separate branch of the U.S. Armed Forces on 18 September 1947 with the passing of the National Security Act of 1947. It is the youngest branch of the U.S. Armed Forces, and the fourth in order of precedence. The USAF is the largest and most technologically advanced air force in the world. The Air Force articulates its core missions as air and space superiority, global integrated intelligence, surveillance, and reconnaissance, rapid global mobility, global strike, and command and control. The U.S. Air Force is a military service branch organized within the Department of the Air Force, one of the three military departments of the Department of Defense. The Air Force, through the Department of the Air Force, is headed by the civilian Secretary of the Air Force, who reports to the Secretary of Defense, and is appointed by the President with Senate confirmation. The highest-ranking military officer in the Air Force is the Chief of Staff of the Air Force, who exercises supervision over Air Force units and serves as one of the Joint Chiefs of Staff. Air Force components are assigned, as directed by the Secretary of Defense, to the combatant commands, and neither the Secretary of the Air Force nor the Chief of Staff of the Air Force have operational command authority over them. Along with conducting independent air and space operations, the U.S. Air Force provides air support for land and naval forces and aids in the recovery of troops in the field. As of 2017[update], the service operates more than 5,369 military aircraft, 406 ICBMs and 170 military satellites. It has a $161 billion budget and is the second largest service branch, with 321,444 active duty airmen, 141,800 civilian personnel, 69,200 reserve airmen, and 105,700 Air National Guard airmen.
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