Boeing B-29 Superfortress X-55 “Limber Richard” (factory number 44-70072) of the 99th Bombardment Squadron / 9th Bombardment Group flying toward Japan with other squadron bombers, 1945. The bombing missions against Japan could last as long as sixteen hours, that's a 3,500 mile or 5632.7km round trip! B-29s took off at dusk, made it to the target before dawn, and after dropping their bombs the return trip was made during the day. Flying at altitude with strong winds, flak, fighting off enemy fighters, the Japanese were able to get their fighters as high as 32,000ft. drop their bombs on the target and that was just getting there. The trip back "invited" more flak, fighters, battle damage wounded and other inflight problems. Did you know that the B-29 carried six tons of bombs and twenty tons of fuel? The B-29 also used about 500lbs or 226.8kg of fuel just to taxi before takeoff!