What we got??? We got 2... count them 2, foreign terrorist attacks on our soil during that time... We haven't gone longer under this system without an attack... The airline security was a failure... That is where we failed, not in pursuing terrorism as law enforcement. I don't advocate airline security going back to the way it was. I believe we've come quite a ways since 9/11, But in too many other aspects, we're just barking up the wrong trees.
As for the people in the WTC, They should've known they were taking a risk. Any time you live or work in such a monument to our system, it is a potential target. Besides that, it was proven over and over to be a target of islamic terrorists. (not only the bombing, but other plots that were either canceled or foiled) So anyone choosing to work in such a place should've known the danger.