The B-17 and the B-29 established Boeing's reputation as a builder of heavy bombers during the WW II era. Once the war was over, their design contributed to the development of subsequent transports and airliners. The B-47 bomber was the first multi-engine swept-wing jet in the world, and the B-52 was America's first long-range swept-wing bomber. The B-52 continues to be an important element of the U.S. bomber fleet. No other bomber in U.S. Military history has remained operational as long as the B-52.