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...
"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).
The cone of the planes are hollow. It's common they hit a single bird and completely cave in. If you slow the video down, the cone doesn't cave in. It just seamlessly goes into the building.
Also, the wings are aluminum. The beams of the building are steel. Once again, as the wings go into the building, they remain intact.