The planes were not flown by alleged hijackers, they were remotely controlled. One of the kingpins of the operation, dual citizen Dov Zakheim, was involved in a company that designed remote control flight systems.
The three towers (including building 7) were rigged weeks ahead of the event, and were brought down in controlled demolitions.
This is the most accurate rundown of the false flag event, arguably the most important event this century, perhaps the most important video posted in all of youtube today:
What about all the people who were on the planes that called on cell phones?