Reply #277: Why add explosives? Because every movie needs explosions.

[petgoat]

If the 9/11 event is to make the whole world different now, it has to be
spectacular. Simply crashing planes into towers is not enough. The
towers must fall. Everyone who works in a tall building (or has family
who works in a tall building) must be made to feel very very vulnerable.

That only happens if the towers fall.