To say that the government new about an impending attack prior to 9/11 and not knowing exactly what they knew about it is unfair. Even if they knew there woud be hijackings on that date, which I doubt they knew, there would have been little they could have done about it. It would have been difficult to ground all flights on that date without concrete proof to justify it. Prior to 9/11 hijackings were nothing more than extortion or transportation. If they had grounded all flights, the administration would have been crucified. In looking back at at what happened prior to the even we must temper that examination with the same beliefs and attutude which was present prior to the attack not the beliefs and attutudes we hold now.