But they didn't need to specifically hit a range of floors, just the two largest buildings in New York. Why do you think they specifically had to hit the floors they did? Also the crashed at different points, Plane 1 93rd-99th floors, Plane 2 77th -85th floors. Both planes hitting high purely due to the nature of New York skyline.
For there to be validity to any claim of an alternative reason for the towers collapsing that day the planes would need to have hit specific pre-determined floors. Theres no way they could have extensively rigged up the whole building not knowing which floor the planes would hit and it not be discovered, but if they targetted a specific range of floors its within credibiity that they could have rented floors at or below their target.
To elaborate, they couldn't have used conventional demolition techniques without a noitceable effect at the base of the tower(s) - all videos from the day taken from the base of the towers show nothing major at the base. Disruption to or below the foundations would have resulted in a very different pattern of collapse, most likely with the building splitting outwards at the top. So the collapse as seen in the videos has to have originated at the point of impact or within 2-3 floors below.
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