Though the fact that this question was even asked, makes me so sad I will share with you my thougths on the matter. I also watched the movie and read the information. First and foremost let us consider this very important fact. To pull something of this magnitude off the government would have to be organized and focused which we know is not true. They would have to keep a secret which we know they can not. They would have to have a motive which contrary to the film they didn't. To suggest the government could even plan something like this is giving them much more credit than they deserve. Who stood to gain from this??? Corporations? NO, the stock market fell after the attacks and hurt every company on earth.
Ask yourself these questions...
Why do I choose to believe in conspiracy theories?
Do I believe the government is capable of an attack on their own people?
and... have I examined all the relevant data on this subject?
The truth is, terrorists were responsible. They murdered innocent American's to create fear and terror. They are the enemy, not the government. We might not agree with what our nation does, but that doesn't make it evil. They are many things we should question, life, faith, and understanding. But this is not one of them.