Underlying all of this is a huge and painful irony that few people ever acknowledge: that pretty much none of the checkpoint rules put in place after the attacks of 9/11 would have prevented those attacks in the first place. The success of the attacks had almost nothing to do with airport security. What weapons the men used was irrelevant. Had boxcutters been banned, they would have used something else. Heck, pencils would have done the job, probably. The only weapon that mattered was the simplest, lowest-tech weapon of all: the element of surprise. What the men exploited was our understanding, at the time, of what a hijacking was and how it was expected to unfold. The “security failure” of 9/11 wasn’t letting boxcutters onto planes. It was a failure of passenger and crew awareness, of cockpit entry protocols, and a total breakdown of communication at the levels of our FBI and CIA, both of which had been tracking the hijackers.