The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It is commonly called the “Bone” (from “B-One”). It is one of three strategic bombers in the U.S. Air Force fleet as of 2020, the other two being the B-2 Spirit and the B-52 Stratofortress. The program was restarted in 1981, largely as an interim measure due to delays in the B-2 stealth bomber program, with the B-2 eventually reaching initial operational capability in 1997. This led to a redesign as the B-1B, which differed from the B-1A by having a lower top speed at high altitude of Mach 1.25, but improved low-altitude performance of Mach 0.96.
The B-1B’s maximum takeoff weight was increased to 477,000 pounds (216,000 kg) from the B-1A’s 395,000 pounds (179,000 kg). The weight increase was to allow for takeoff with a full internal fuel load and for external weapons to be carried. Rockwell engineers were able to reinforce critical areas and lighten non-critical areas of the airframe, so the increase in empty weight was minimal. To deal with the introduction of the MiG-31 equipped with the new Zaslon radar system, and other aircraft with look-down capability (which reduced the B-1s low-flying advantage), the B-1B’s electronic warfare suite was significantly upgraded.
In the early 1990s, following the Gulf War and concurrent with the disestablishment of SAC and its reassignment to the newly formed Air Combat Command, the B-1B was converted to conventional bombing use. It first served in combat during Operation Desert Fox in 1998 and again during the NATO action in Kosovo the following year. The B-1B has supported U.S. and NATO military forces in Afghanistan and Iraq. The Air Force had 62 B-1Bs in service as of 2016. The B-1B is expected to continue to serve into the 2030s, with the Northrop Grumman B-21 Raider to begin replacing the B-1B after 2025. The B-1s in inventory are planned to be retired by 2036.