The B-1 Lancer is a swing-wing bomber intended for high-speed, low-altitude penetration missions. By the end of 1977, three Rockwell International B-1As had made 118 flights with more than 21 hours at supersonic speeds. The next version was the B-1B. The B-1B differed from the B-1A in several ways. The requirement for Mach 2.2 flight was reduced to Mach 1.25, simplifying the inlet and over-wing fairing structure. The maximum gross take-off weight was increased from 395,000 to 477,000 poundsand the radar cross section was reduced an order of magnitude. The B-1B Lancer first flew Oct. 18, 1984, could operate at 60,000 feet and had a range of more than 7,000 miles. The B-1B holds 61 world records for speed, payload and distance.