U.S. Army Air Corps Gunnery Schools were World War II organizations for training fighter pilots and bomber crewmen at several United States Army Airfields and gunnery ranges (3 schools opened in 1941). "Flexible Gunnery" training developed diverse skills for various aircraft and differing positions within bombers, e.g., waist gunner, rear gunner, etc. "The number of graduates had reached 19,789 by 7 July 1943, with another 57,176 men completing the course by the end of the year." At Las Vegas Army Airfield 600 gunnery students and 215 co-pilots were graduated every five weeks at the height of World War II. Training started on the ground using mounted shotguns with fixed arcs of fire, and then shotguns mounted on the backs of trucks, which were driven through a course. Then the students went up in the bombers, shooting at targets pulled by other aircraft.