- The B-1/12c is this timeline's designation for the B-1R.
The B-1A was the original B-1 design with variable engine intakes and Mach 2.2 top speed. Four prototypes were built; no production units were manufactured.
The B-1B is a revised B-1 design with reduced radar signature and a top speed of Mach 1.25. It was otherwise optimized for low-level penetration. A total of 244 B-1Bs were built.
The B-1C is an upgrade of existing B-1B aircraft. The B-1C is fitted with advanced radars, air-to-air missiles, and newer more powerful engines. Existing external hardpoints were modified to allow multiple conventional weapons to be carried, increasing overall loadout. For air-to-air defense, an Active Electronically Scanned Array (AESA) radar would be added and some existing hardpoints modified to carry air-to-air missiles. If needed, it can escape from unfavorable air-to-air encounters with its Mach 2+ speed. Few aircraft are currently capable of sustained speeds over Mach 2.