First, they had to send several men through pilot training, at least enough to pull off the attacks. Several men (4 to 8) were sent to the US to go through the training. That takes time and money. Flight training is neither cheap nor instantaneous. If memory serves, they were here for around a year, long enough to get a private pilot's license and perhaps an instrument rating.

They also needed resources to scout out the targets and take practice flights. On at least one occassion, they tested airline security by taking flights and seeing how hard it was to smuggle on the box cutters and get to the cockpit. They also had to get the other hijackers, the muscle, into America and trained for their part in the attacks.

I'd wager the whole 9-11 attack probably didn't cost over a million dollars. That's certainly within the resources of someone like Osama bin Laden. There was a lot of planning to coordinate the hijackings, there may have been need to obtain false passports, etc. Little or none of this would've required active governmental support, but that support would've made it easier.

I fully agree that if someone wanted to, he could conduct all sorts of small scale attacks here in the US. A large scale attack requires resources and skill, but little attacks could happen every day. We've been fortunate that this hasn't happened.

Al Queda has been behind terrorist attacks that have killed several thousand people. We'd be foolish to ignore them, but they're not the only terrorist group out there.