Yeager enlisted as a private in the U.S. Army Air Forces (USAAF) on September 12, 1941, and became an aircraft mechanic at George Air Force Base, Victorville, California. At enlistment, Yeager was not eligible for flight training because of his age and educational background, but the entry of the U.S. into World War II less than three months later prompted the USAAF to alter its recruiting standards. Yeager had unusually sharp vision (a visual acuity rated 20/10), which once enabled him to shoot a deer at .