Which, despite the popular misconception, had nothing to do with the windows the passengers could see through. There were other "windows" for antennas which were internally mounted to avoid their parasitic drag.

The fuselages failed at an escape hatch and a joint where a box had been inserted to internally mount an antenna. The skin was cut too close to the side of the box instead of having the proper overlap. The fact they were running the thing at 8.25 PSI had a lot to do with the failure as well.