Following the withdrawal of the UK, McDonnell Douglas extensively redesigned the earlier AV-8A Harrier to create the AV-8B. While retaining the general layout of its predecessor, the aircraft uses a new wing, an elevated cockpit, a redesigned fuselage, one extra hardpoint per wing, and other structural and aerodynamic changes. The aircraft is powered by an upgraded version of the Pegasus, which gives the aircraft its V/STOL ability. The AV-8B made its maiden flight in November 1981 and entered service with the USMC in January 1985. Later upgrades added a night-attack capability and radar. This resulted in the AV-8B(NA) and AV-8B Harrier II Plus, respectively. An enlarged version named Harrier III was also studied, but was not built. The UK, through British Aerospace, re-joined the improved Harrier project as a partner in 1981. After corporate mergers in the 1990s, Boeing and BAE Systems have jointly supported the program. Approximately 340 aircraft were produced in a 22-year production program that ended in 2003.