The Army created the first antecedent of the USAF in 1907, which through a succession of changes of organization, titles, and missions advanced toward eventual separation 40 years later. The Air Force came of age in World War II. Only the infantry suffered more enlisted casualties than the Army Air Forces: almost 68,000 enlisted men died. In practice, the USAAF was virtually independent of the Army during World War II, but officials wanted formal independence. The USAF became a separate military service on September 18, 1947, with the implementation of the National Security Act of 1947. The Act created the United States Department of Defense, which was composed of three subordinate departments, namely the Department of the Army, the Department of the Navy and a newly-created Department of the Air Force. Prior to 1947, the responsibility for military aviation was shared between the Army (for land-based operations), the Navy (for sea-based operations from aircraft carriers and amphibious aircraft), and the Marine Corps (for close air support of infantry operations).

The predecessor organizations of today's USAF are:

• Aeronautical Division, U.S. Signal Corps (August 1, 1907 to July 18, 1914)
• Aviation Section, U.S. Signal Corps (July 18, 1914 to May 20, 1918)
• Division of Military Aeronautics (May 20, 1918 to May 24, 1918)
• U.S. Army Air Service (May 24, 1918 to July 2, 1926)
• U.S. Army Air Corps (July 2, 1926 to June 20, 1941) and
• U.S. Army Air Forces (June 20, 1941 to September 17, 1947)

Recent history of US Air Force

Since 2005, the USAF has placed a strong focus on the improvement of Basic Military Training (BMT). While the intense training has become longer it also has shifted to include a deployment phase. This deployment phase, now called the BEAST, places the trainees in a surreal environment that they may experience once they deploy. While the trainees do tackle the massive obstacle courses along with the BEAST, the other portions include defending and protecting their base of operations, forming a structure of leadership, directing search and recovery, and basic self aid buddy care. During this event, the Military Training Instructors (MTI) act as mentors and enemy forces in a deployment exercise.

In 2007, the USAF undertook a reduction-in-force. Because of budget constraints, the USAF planned to reduce the service's size from 360,000 active duty personnel to 316,000. The size of the active-duty force in 2007 was roughly 64% of that of the USAF at the end of the Gulf War in 1991. However, the reduction was ended at approximately 330,000 personnel in 2008 to meet mission requirements. These same constraints have seen a sharp reduction in flight hours for crew training since 2005 and the Deputy Chief of Staff for Manpower and Personnel directing Airmen's Time Assessments.

On June 5, 2008, Secretary of Defense Robert M. Gates, accepted the resignations of both the Secretary of the Air Force, Michael W. Wynne, and the Chief of Staff of the United States Air Force, Gen. T. Michael Moseley. Gates in effect fired both men for "systemic issues associated with declining Air Force nuclear mission focus and performance". This followed an investigation into two embarrassing incidents involving mishandling of nuclear weapons, and were also the culmination of disputes between the Air Force leadership and Gates. To put more emphasis on nuclear assets, the USAF established the nuclear-focused Air Force Global Strike Command on 24 October 2008.

On June 26, 2009, the USAF released a force structure plan that cuts fighter aircraft and shifts resources to better support nuclear, irregular and information warfare. On July 23, 2009, The USAF released their Unmanned Aerial System Flight Plan, detailing UAV plans through 2047. One third of the planes that the USAF plans to buy in the future are to be unmanned.

In recent years the USAF has fumbled several high profile aircraft procurement projects, such as the failure to make the case for the Next-Generation Bomber, the failure to control costs on the Lockheed Martin F-22 Raptor and the decade of failures on the KC-X program. Winslow Wheeler has written that this pattern represents "failures of intellect and -- much more importantly -- ethics."

Conflicts

• World War I as Aviation Section, U.S. Signal Corps
• World War II as United States Army Air Forces
• Cold War
• Korean War
• Vietnam War
• Operation Eagle Claw (1980 Iranian Hostage Rescue)
• Operation Urgent Fury (1983 US Invasion of Grenada)
• Operation El Dorado Canyon (1986 US Bombing of Libya)
• Operation Just Cause (1989-1990 US Invasion of Panama)
• Operation Desert Shield and Operation Desert Storm (1990-1991 Persian Gulf War)
• Operation Southern Watch (1992-2003 Iraq No-Fly Zone)
• Operation Deliberate Force (1995 NATO bombing in Bosnia and Herzegovina)
• Operation Northern Watch (1997-2003 Iraq No-Fly Zone)
• Operation Allied Force (1999 NATO bombing of Yugoslavia)
• Operation Enduring Freedom (2001–present Afghanistan War)
• Operation Iraqi Freedom (2003–2010 Iraq War)

Humanitarian operations

The USAF has also taken part in numerous humanitarian operations. Some of the more major ones include the following:

• Berlin Airlift (Operation Vittles), 1948-1949
• Operation Safe Haven, 1956-1957
• Operations Babylift, New Life, Frequent Wind, and New Arrivals, 1975
• Operation Provide Comfort, 1991
• Operation Sea Angel, 1991
• Operation Provide Hope, 1992–1993
• Operation Unified Assistance, December 2004 - April 2005
• Operation Unified Response, January 14, 2010–present