Ground crews were responsible for keeping the aircraft of WWII in safe flying condition. Ground crew members made repairs to aircraft, as well as handling routine maintenance. As soon as a plane lands, the ground crew went to work - checking landing gear, refilling fuel tanks, examining the wings, and making any necessary repairs. Aside from regular AAF soldier schooling, ground crews were also highly trained in mathematics, mechanics, and machine shop skills. The ground crew's job was truly to "keep 'em flying."