Edwards Air Force Base, U.S. military installation, 301,000 acres (121,805 hectares), S Calif., NE of Lancaster; est. 1933. It is one of the largest air force bases in the United States and has the world's longest runway. The base houses the Air Force Flight Test Center, which researches and develops aerospace weapons and rocket-propulsion systems, and the National Aeronautical and Space Administration's Flight Research Center. The base is also the proving ground for military aircraft. It was the landing point for a number of space shuttle missions; on Sept. 5, 1983, the Challenger made the first nighttime landing of a spacecraft there.