17 Flying Fortress
One of the most renowned combat aircraft of WW II, America's first all-metal, four-engine heavy bomber aircraft, the Boeing B-17 Flying Fortress was primarily utilized in daylight raids to conduct a precision strategic bombing campaign targeting German industrial and civilian targets. In the Pacific theatre, it was used to destroy Japanese airfields and shipping.
Because of their long-range capability and heavy armament, formations of B-17s often flew into battle without a fighter escort. The G variant, for example, carried a healthy complement of 13 .50 calibre machine guns, and was thus very capable of defending itself. By 1944 the B-17s were being accompanied by squadrons of P-51 Mustangs, which allowed the bomber crews to concentrate on their primary duty, pounding aircraft and munitions factories, as well as important psychological targets such as Berlin.
The bombing raids on Germany by the U.S. 8th Air Force and RAF's Bomber Command ripped the heart out of Germany's industrial production. By September 1944, the B-17s had not only 'delivered' 500,000 tons of the 1.5 million tons of bombs dropped on Germany, but additionally the airgunners had fired 99 million rounds of ammunition during those missions, downing over 20,000 German planes in the process. Over 12,000 B-17s were built during the war and nearly 250,000 Americans and allied aircrew flew in them, 46,500 of these brave men being either killed or wounded. The B-17 remains one of the defining bombers of WWII.