I firmly believe that there was not another 9/11-style attack because 9/11 didn't do shit of what the bad guys wanted. Simply, it is not cost-effective. I find it very hard to believe that the security theater of the TSA would have any chance of denying well-financed and trained attackers. Yeah, it probably works against the stupid kind of kidnappers from the '70s ("I want 1 million dollars in non-marked notes, refuel and want to go to Havana, and while we're at it, I want my girlfriend who is in jail because of drug charges, to be released and brought to this plane"), but at what cost?