I read about this a long time ago, never seen this animation though.
This subject might be a bit delicate to discuss, the whole 9/11 issue is rather complicated. I think as a personal opinion that whatever crashed on the pentagon or made it explode was never a plain at all. It might well have been a missile, but that raises the question "who did it?"
It's easy to blame Al Qaida and angry islam extremists, but I think it isnt that simple.