By the 21st century, the Boeing B-52 was in its fifth decade of operational service. The eight-engine, 390,000-pound jet was the country's first long-range, swept-wing heavy bomber. It began as an intercontinental, high-altitude nuclear bomber, and its operational capabilities were adapted to meet changing defense needs. Production versions of the B-52A were B-52Bs, with more weight and larger engines. Some had photographic reconnaissance or electronic capsules in their bomb bays and were redesignated RB-52Bs. The B-52s increased in range, power and capability with each variant. The B-52H made its first flight March 6, 1961, and is still in service. In all, 744 B-52s were produced by Seattle, Wash., and Wichita, Kan., plants between 1952 and 1962.