The Boeing B-29, the most technologically advanced airplane produced during World War II, first flew Sept. 21, 1942. At 105,000 pounds, it was the world's heaviest production airplane. It was the first bomber with crew-cabin pressurization and remotely controlled power turrets. A total of 3,970 B-29s were built, with improvements added to the bombers as they went through the production line as data came in from pilots in action. World War II ended when two B-29s, the Enola Gay and Bockscar dropped atomic bombs on Hiroshima and Nagasaki.