The Fairchild Republic A-10 Thunderbolt II is a single-seat, twin-turbofan, straight-wing, subsonic attack aircraft developed by Fairchild Republic for the United States Air Force (USAF). In service since 1976, it is named for the Republic P-47 Thunderbolt, a World War II-era fighter-bomber effective at attacking ground targets, but commonly referred to as the "Warthog" or "Hog". The A-10 was designed to provide close air support (CAS) to friendly ground troops by attacking armored vehicles, tanks, and other enemy ground forces; it is the only production-built aircraft designed solely for CAS to have served with the U.S. Air Force. Its secondary mission is to direct other aircraft in attacks on ground targets, a role called forward air controller-airborne; aircraft used primarily in this role are designated OA-10.