Actually, you're all wrong.
It will be (like stormbind said) an amazing three-hour epic that intertwines the action of a passenger on the Pennsylvania plane, someone working in the World Trade Center, someone working in the Pentagon, Bush and the politicians, and some soldiers who stand around watching 9/11 happen, get all pissed off, and it ends with them going to Afgahnistan to kick some ass.
I should write this ****.
EDIT: The moment that will not be in the movie:
My father running out of his office building with the steady flow of people over the bridge. Some man, in a crowd, yells "Bomb!" to try to get up to the front. After everyone ducks down, some man stands up and punches him in the face.
Actually, that might get in there. The whole punching of the face part would be good to get the crowd cheering.