of the Air Force. Prior to 1947, the responsibility for military aviation was shared between the Army Air Forces and its predecessor organizations (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 Marine Corps operations). The 1940s proved to be important for military aviation in other ways as well. In 1947, Air Force Captain Chuck Yeager broke the sound barrier in his X-1 rocket-powered aircraft, beginning a new era of aeronautics in America. Antecedents The predecessor organizations in the Army of today's Air Force are: Aeronautical Division, Signal Corps (1 August 1907 – 18 July 1914) Aviation Section, Signal Corps (18 July 1914 – 20 May 1918) Division of Military Aeronautics (20 May 1918 to 24 May 1918) U.S. Army Air Service (24 May 1918 to 2 July 1926) U.S. Army Air Corps (2 July 1926 to 20 June 1941) and U.S. Army Air Forces (20 June 1941 to 18 September 1947) 21st century During the early 2000s, two USAF aircraft procurement projects took longer than expected, the KC-X and F-35 programs. As a result, the USAF was setting new records for average aircraft age. Since 2005, the USAF has placed a strong focus on the improvement of Basic Military Training (BMT) for enlisted personnel. 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 simulated combat 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 opposing forces in a deployment exercise. In 2007, the USAF undertook a Reduction-in-Force (RIF). 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 what the USAF was at the end of the first Gulf War in 1991. However, the reduction was ended at approximately 330,000 personnel in 2008 in order to meet the demand signal of combatant commanders and associated mission requirements. These same constraints have seen