Claim: Little Boy was dropped by a plane.

The Boeing B-29 Superfortress is a four-engine propeller-driven heavy bomber designed by Boeing which was flown primarily by the United States during World War II and the Korean War . It was one of the largest aircraft operational during World War II and featured state of the art technology . It was the single most expensive weapons project undertaken by the United States in World War II , exceeding the cost of the Manhattan Project by between 1 and 1.7 billion dollars . Innovations introduced included a pressurized cabin , dual-wheeled , tricycle landing gear , and a remote , computer-controlled fire-control system that directed four machine gun turrets that could be operated by a single gunner and a fire-control officer . A manned tail gun installation was semi-remote . The name `` Superfortress '' continued the pattern Boeing started with its well-known predecessor , the B-17 Flying Fortress . Designed for the high-altitude strategic bomber role , the B-29 also excelled in low-altitude nighttime 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 .   Because of the B-29 's advanced design , unlike many other World War II-era bombers , the Superfortress 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 as the Washington until phasing out the type in 1954 . 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 the B-50 Superfortress -LRB- the first aircraft to fly around the world non-stop -RRB- which was essentially a re-engined B-29 . The type was retired in the early 1960s . The B-29 production total was 3,970 aircraft . Dozens of B-29s remain as static displays but only two examples , Fifi and Doc , have been restored to flying status ; with Doc flying again for the first time from McConnell AFB on July 17 , 2016 .   A transport developed from the B-29 was the Boeing C-97 Stratofreighter , first flown in 1944 , followed by its commercial airliner variant , the Boeing Model 377 Stratocruiser in 1947 . This bomber-to-airliner derivation was similar to the B-17 / Model 307 evolution . In 1948 Boeing introduced a tanker variant of the B-29 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 Stratocruiser is the GuppyMini GuppySuper Guppy which remain in service today with operators including NASA .