US Air Force
United States Air Force
The United States Air Force ( USAF ) is the aerospace branch of the United States armed forces and one of the seven uniformed services . Formerly part of the United States Army , the USAF was formed as a separate branch of the military on September 18 , 1947 .  The USAF is the largest and most technologically advanced modern air force in the world, with over 9,000 aircraft in service and about 352,000 men and women on active duty . 
Since World War I , the USAF and its predecessors have taken part in military conflicts throughout the world. The USAF is currently planning a massive Reduction-in-Force (RIF). Because of budget constraints, the USAF will reduce the service's current size by 40,000 full time equivalent positions by 2011. This amounts to roughly 35,000 active duty positions and will be added to the reserves. 
According to the National Security Act of 1947 which created the Air Force, "In general the United States Air Force shall include aviation forces both combat and service not otherwise assigned. It shall be organized, trained, and equipped primarily for prompt and sustained offensive and defensive air operations. The Air Force shall be responsible for the preparation of the air forces necessary for the effective prosecution of war except as otherwise assigned and, in accordance with integrated joint mobilization plans, for the expansion of the peacetime components of the Air Force to meet the needs of war."
The stated mission of the USAF today is to "deliver sovereign options for the defense of the United States of America and its global interests — to fly and fight in Air, Space, and Cyberspace". 
Not all of the United States' military combat aircraft are operated by the USAF. The United States Army operates its own helicopters, mostly for support of ground combatants. The Navy is responsible for the aircraft operating on its aircraft carriers and Naval air stations , and the Marine Corps operates its own combat and transport aircraft. The Coast Guard also maintains transport and search-and-rescue aircraft, which may be used in a combat and law enforcement role. All branches of the U.S. military operate helicopters.