Site 1, at the northwest corner of the airfield, is operated by Boeing, which uses it for UAV programs and other advanced and classified aviation projects. The site was developed by North American Aviation in 1952, to build fighter jets. Starting in the 1970s, Rockwell developed and built B-1 bombers here, a plane which still serves as the nation’s only supersonic heavy bomber. Rockwell also built all five of the Space Shuttles, using an assembly building at Site 1. Boeing acquired Rockwell in 1996, and took over the site as its High Desert Assembly Integration and Test facility. Boeing developed the X-37 here, a smaller reusable robotic space shuttle that the Air Force has used for secretive space missions.