US Air Force B-1B Lancer bomber model. The B-1B is a multi-role, long-range bomber, capable of flying intercontinental missions without refueling, then penetrating present and predicted sophisticated enemy defenses. It can perform a variety of missions, including that of a conventional weapons carrier for theater operations. Through 1991, the B-1 was dedicated to the nuclear deterrence role as part of the single integrated operational plan (SIOP). Converting the B-1B to the conventional role was a gradual process, beginning in 1993 and culminating in October 1997 when the 7th Bomb Wing at Dyess AFB flew the last nuclear mission.