Lots of easter eggs in this interview. Silverstein etc... but listen to Trump's answer to the question asked at (5:14) about the integrity of the buildings...

https://youtu.be/PcKlPhFIE7w

"How could a plane, even a plane, even a 767 or 747 or whatever it might have been, how could it possibly go through this steel? I happen to think they not only had a plane, but had bombs that exploded almost simultaneously, because I just can't imagine anything being able to go through that wall..."

"It just seemed to me that, to do that kind of destruction, is even more than a big plane, because you're talking about taking out steel, the heaviest calibre steel that was used on a building. I mean these buildings were rock solid..."

Also worth noting the steel column vaporising at (2:03).