Was there a design flaw or would any building of that height have failed?
In: Engineering
[This](https://www.youtube.com/watch?v=1NkBfLBov5Q) video goes into detail what happened.
TLDW: Unlike many other buildings the outer structure of the WTC was load-bearing. It had a very stiff center and the floors rested on steel beams between that and the load-bearing outer steel girders. When the plane hit the fire proofing of the flooring got demolished. That allowed the fire to heat up the floor steel beams much faster. Steel gets weaker the hotter it is and the floors started to sag. Eventually some floors broke off and crashed on the still strong floors below. That also made them sag but since they were still strong they didn’t bend as much but pull the outer shell inwards, creating a bulge. In the video they demonstrate that with a can of coke which can carry a lot of weight but as soon as they artificially create a bulge it collapses. That happened also at the WTC. Once the bulge started to collapsed inwards the same thing happened over and over again at each floor, just with tons and tons of more weight.
It was not a design flaw as they considered an impact in the planning stage. However, at the time of the planning the largest plane they could expect was a fraction in size and weight of the planes that eventually hit. They could not have planned for such a difference.
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