I've wondered why they haven't done that before. Forget about taking a plane down, or flying into a building.
Have 20 individuals at 20 airports all approach the processing line, timed to arrive at the metal detector/x-ray chute at noon. Scream the usual "aloha cracker" (or whatever those crazy fucks say), pull out the bomb from their carry on, and detonate it before anyone can stop them.
Instantly, every airport is notified about this threat, and now everyone gets screened before they even get to the airport.
If they want to fuck with the west, that is how they could do it.
The fact that this has not happened (nor have we heard of a such a plot being defused) makes it pretty clear that the real threat is the TSA itself, and "terrists" are simply an Emmanuel Goldstein type boogeyman used to keep everyone in line and their mouths shut.