You're not the only one. If I recall correctly, wasn't there (for lack of a better word) "intelligence" which had heard about terrorists planning to hi-jack commercial jets to be used as suicide bombs, but instead of 4 planes the original plan was for about a dozen planes to be the number that the terrorists were shooting for? It would be almost poetic if the one thing that saved the Sears Tower and TransAmerica building was the typical flight delays that everyone who flies frequently often complains about.
I do have to give the air traffic controllers their due for how they were able to get all of those thousands of planes out of the sky and onto the ground as fast as they did, and without any accidents in the process. I wonder how different things might have been if Reagan had not fired all of those air traffic controllers when they went on strike in the 80's.
Reagan was right in canning them. Some government jobs just shouldn't be strike-sensitive. Imagine if PATCO has triumphed and Sept. 11th was in the middle of an ATC system strike, with management personnel operating the ATC system. Disaster would have been an understatement.