Text from an advertisement in October 1943 issue of Aviation magazine: NO ACHILLES HEEL (photo of badly damaged B-17 in flight) This slashed-in-two Flying Fortress theoretically should not fly. There had been stiff fighter opposition. In the melee a Messerschmitt, crazily out of control, crashed into it. The German plane was destroyed on impact. The Fortress' fuselage was ripped diagonally from top to bottom. Control surfaces were carried away. The tail gunner, suddenly imperiled in his wabbling section, crawled forward over the narrow floor structure that held the parts together. And the fortress flew steadily for an hour and three-quarters- back to her base for a perfect landing! Often the question is asked about Boeing Fortresses: "How can they do it?" One Fortress came home with 2000 bullet holes, and big areas of both wing sections shot away. Another had a hole in the fin "large enough for the navigator to walk through." Others have come in with rudder and elevator controls sheared by gunfire. How can they do it? One reason is Boeing design. The Fortress has no Achilles heel, not highly vulnerable spot for the enemy to attack. No single structural member has to carry the entire load for its section; even when large portions of the plane are badly damaged, the Fortress usually is strong enough to remain aloft, fight off its enemies, and return home. There are other reasons, of course- many of them. But they all stem from what has been termed the integrity of Boeing products. Soundly and conservatively engineered, honestly built, these products have always done more than has been expected of them. True today, it likewise will be true in peacetime tomorrow... if it's "Built by Boeing" its bound to be good. Boeing Designers of the Flying Fortress - The Stratoliner - Pan American Clippers