In 1937 the Boeing Aircraft Company built America's first all-metal, four-engine heavy bomber, the legendary B-17 Flying Fortress. Bristling with 13 0.5 machine guns, and with an average bomb load of 6,000 pounds, the "Forts" took on the worst the Luftwaffe had to offer. Flying in formations of up to 1,000 bomber daylight raids, the B-17s attacked some of the most heavily defended targets in occupied Europe. Suffering unprecedented losses, the young American airmen in their B-17s helped turn the tide of the war in Europe by destroying the Nazi war machine.