This is exactly how 911 was pulled off. I am very much convinced that the new group of bombers ready to go in USA are as stupid as Padilla and Reid the shoe bomber. Picking out 19 guys to inflict 911 was a miracle in body power. Those 19 were the creme of the creme so to speak. Will take years before they can find anything similar.
9/11 involved more than 30 hijackers. Recall reports that a plane in London was held on the ground and that a probable hijack team fled. Other reports indicated hidden weapons were found on other planes in the U.S.
Al Quaida planners know that all their plans will not work. Hence the multiple threat and multi-layered threat they design in to their plans.
So the B team from 9/11 is still out there. Plus they trained thousands from which they recruited the 9/11 hijackers. Al Quaida is attenuated, certainly, but they are not done.