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. Boeing built 8,584 Kaydets, in all versions, plus the equivalent of 2,000 more in spares, between 1936 and 1944.