I agree with Patrick Smith, author of Ask the Pilot, the nature of terror attack is always surprise. 9/11 is not going to happen again and airport security has nothing to do with it. No group of passengers or pilots will let anyone or a group capture a passenger plane.
Remember the hundred captures that were hijackings to Cuba? People had the experience of surviving so they tolerated the hijackings. Got it. 9/11 was a surprise.
Surprise, the Fundamentalist (Muslim and Lefty) who took over the Greater Seattle Jewish Welfare office got through security by taking a 13 year old girl hostage. Oops, surprise. Security gates don't work any more. Not at all, fini.