I think a lot of people figured out that the collapse of the towers surprised the terrorists as much as it surprised us. A lot of their attack came off from sheer luck and a weak spot in our security.

BTW, when the terrorists hijacked the airliners, it was LEGAL to carry a knife (less than 4" blade) on an airplane. I used to carry my Swiss Army Knife on flights all the time. It was in my belt pack, X-rayed, noticed, and passed. Once someone opened the bag and looked at it.

The sad fact is that before Sept. 11, even if we had MIT graduates working airline security, each paid 100,000 a year, with bomb detectors, mass luggage X-rays, guards at every gate, and the archangel Michael standing in front of the boarding ramp with a flaming sword...

nothing would have been different.