Reply #47: that doesn't explain how 80+ floors of undamaged structure gave way like they weren't even there

[LongDistanceRunner]

if they had put up any resistance, massive amounts of friction would have been created and the buildings would have fallen much slower than freefall speed.

as it was, the fall took the same amount of time as if the top 20+ floors had fallen through thin air.

something happened to the cores of those buildings. that much is evident. and it wasn't just at the point of plane impact.