Yes, 9/11 was successful because, as of 9/10/01, hijacking was one of the safest, most trouble-free crimes by which to be victimized. Airline crews and passengers were recommended to follow hijacker's orders, and typically the worst thing that happened was that the passengers and crew got to take an unexpected side trip. All the implements the terrorists involved in those attacks used were perfectly legal to carry on planes as of the morning of 9/11/01.

In my conversations with colleagues who were contract screeners before TSA, I'm not sure the creation of TSA was necessary. Prevailing opinion among them seems to be that the beneficial changes could have been enacted among the old contract screening forces, and would have gotten pretty much the same results. I didn't follow aviation security issues very closely before 9/11/01, so I can't really say that I have the best informed opinion on this matter.

Also, I believe that the patriots of United 93 showed us exactly what would happen in the event of a modern hijacking. The only difference between them and the passengers of the other flights is that they got information about what was really happening early enough to do something about it. They probably saved countless lives, possibly including my own. (God bless them.) That's part of why I take real security so seriously, and why I am intolerant of the "security theater."