The B-29 Superfortress is a four-engine propeller-driven heavy bomber designed by Boeing that was flown primarily by the United States toward the end of World War II and during the Korean War. It was one of the largest aircraft to have seen service during World War II and a very advanced bomber for its time, with features such as a pressurized cabin, an electronic fire-control system, and remote-controlled machine-gun turrets. The name "Superfortress" was derived from that of its well-known predecessor, the B-17 Flying Fortress. Although designed as a high-altitude strategic bomber, and initially used in this role against the Empire of Japan, these attacks proved to be disappointing; as a result the B-29 became the primary aircraft used in the American firebombing campaign, and was used extensively in low-altitude night-time incendiary bombing missions. One of the B-29's final roles during World War II was carrying out the atomic bomb attacks on Hiroshima and Nagasaki.
Unlike many other World War II-era bombers, the B-29 remained in service long after the war ended, with a few even being employed as flying television transmitters for the Stratovision company. The B-29 served in various roles throughout the 1950s. The Royal Air Force flew the B-29 and used the name Washington for the type, replacing them in 1953 with theCanberra jet bomber, and the Soviet Union produced an unlicensed reverse-engineered copy as the Tupolev Tu-4. The B-29 was the progenitor of a series of Boeing-built bombers, transports, tankers, reconnaissance aircraft and trainers including theB-50 Superfortress (the first aircraft to fly around the world non-stop) which was essentially a re-engined B-29. The type was finally retired in the early 1960s, with 3,970 aircraft in all built. While dozens of B-29s have survived through today as static displays, only one, Fifi, remains on active flying status.
A transport derived from the B-29 was the C-97, first flown in 1944, followed by its commercial airliner variant, the BoeingModel 377 Stratocruiser in 1947. This bomber-to-airliner derivation was similar to the B-17/Model 307 evolution. The tanker variant of the B-29 was introduced in 1948 as the KB-29, followed by the Model 377-derivative KC-97 introduced in 1950. A heavily modified line of outsized-cargo variants of the B-29-derived Stratocruiser is the Guppy / Mini Guppy / Super Guppywhich remain in service today with operators such as NASA.