Development started under the “Advanced Technology Bomber” (ATB) project during the Carter administration; its expected performance was one of the President’s reasons for the cancellation of the Mach 2 capable B-1A bomber. The ATB project continued during the Reagan administration, but worries about delays in its introduction led to the reinstatement of the B-1 program. Program costs rose throughout development. Designed and manufactured by Northrop, later Northrop Grumman, the cost of each aircraft averaged US$737 million (in 1997 dollars). Total procurement costs averaged $929 million per aircraft, which includes spare parts, equipment, retrofitting, and software support. The total program cost, which included development, engineering and testing, averaged $2. 1 billion per aircraft in 1997.