Originally proposed in 2004 as the B-1R (R for "regional), the Boeing B-1C was an upgrade of 25 existing B-1B aircraft with advanced radars, air-to-air missiles, Pratt & Whitney F119 engines, and a new V-tail. This variant had a top speed of Mach 2.2, but with 20% less range than B-1B.
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 was installed and some existing hardpoints modified to carry air-to-air missiles. If needed, the B-1C could escape from unfavorable air-to-air encounters with its Mach 2+ speed. At the time, few aircraft were capable of sustained speeds over Mach 2.