The Beechcraft AT-11 Kansan was the standard bombing trainer in World War II and trained more than 90 percent of the more than 45,000 Army Air Force bombardiers. One of several military versions of the Beechcraft Model 18 Commercial Transport, it was uniquely configured for bombardier training with a transparent nose, a bomb bay with internal bomb racks, and an upper turret for aerial gunnery instruction. In 1943, the Army Air Force set a minimum proficiency standard of a 22 percent hit rate on targets, and student bombardiers normally used 100-pound sand-filled practice bombs to reach it. A bomb run involved continuous evasive action within a ten-mile radius of the target, followed by straight and level flight for the last 60 seconds before release for aiming. After September 1943, these missions were usually flown with the Norden Bomb sight and the C-1 automatic pilot, allowing the student bombardier to control the aircraft during the final critical phase before release. This aircraft is one of the 1,582 ordered by the Army Air Force between 1941 and 1945, and its markings represent AT-11s used at Barksdale Field from 1945 through 1949. Barksdale was the second home of the Army Air Corps Bombardier School from 1940 to 1942, and its alumni included Major Kermit K. Beahan, the bombardier who dropped the last atomic weapon of World War II.