For learning more about the structural lessons to be learned why not go and look up De Havilland Comet on the web. The designers put in round windows for what was the world's first jet airliner but the airlines said their customers wanted bigger squarer windows to see out of. Only after a series of horrenous crashes was it discovered how the weak points at corners caused metal fatigue and failure. The British air industry never recovered from this and Boeing especially took the lead in airliner technology. More was learnt from this about metal fatique than from any other individual project ... and the testing was done by submerging the fuselage in water repeatedly until it failed.