By 1943 the U.S. 8th Air Force - known as the U.S. Army Air Corps – had 130 bases in England most in the east with the B-17 Flying Fortress the main heavy bomber. The basic mission of the 8th Air Force was to bomber Germany’s cities and industry, just like the Luftwaffe had done to England during the Battle of Britain. B-17 ground crews maintained over 1,000 aircraft system so the crew of 10 could fly and fight the plane. Air attacks against Germany and German held Europe were virtually daily with the American air forces attacking during the day and British air power striking at night. Bombers fought their way to targets through flak and fighters suffering high losses, even with fighter escorts. While German air defenses (ground and fighter) inflicted high losses, no mission was ever turned back by enemy action. By wars end, the 8th Air Force suffered 47,000 casualties and lost 5100 (according to published sources) aircraft while flying over 440,000 sorties.