The B-1 Lancer is an American supersonic strategic bomber with variable-sweep wings. Its origins began in the 1960s as a supersonic bomber with sufficient range and payload to replace the B-52 Stratofortress. The B-1B production version has been in service with the United States Air Force (USAF) since 1986. The Lancer serves as the supersonic-capable component of the United States's long-range bomber force with the B-52 and the B-2 Spirit. As with several official popular names, the Lancer is commonly called the Bone within the USAF. With the retirement of the EF-111 Raven in 1998, and the F-14 Tomcat in 2006, the B-1B is the last swing-wing aircraft remaining in the U.S. inventory.