Absolutely had to. WTC 1 & 2 featured a steel exoskeleton around the perimeter of the building as opposed to steel members supporting from the stair and elevator core. There is no way in hell those planes pierced the exoskeleton independently - the planes would have been crushed like a tuna can.
Without strong steel beams, you cannot hold up that kind of a large building. Try using aluminum beams for support a building and see what happen. I would like to know.
Absolutely had to. WTC 1 & 2 featured a steel exoskeleton around the perimeter of the building as opposed to steel members supporting from the stair and elevator core. There is no way in hell those planes pierced the exoskeleton independently - the planes would have been crushed like a tuna can.
Without strong steel beams, you cannot hold up that kind of a large building. Try using aluminum beams for support a building and see what happen. I would like to know.