Thanks for the link. That discusses false positives, not false negatives. Obviously, you'd want to minimize false positives, as they result in unnecessary procedures to resolve the alarm, but false negatives are the bigger problem.

You might remember that the MMW AIT scanners were originally read by an operator in a remote room instead of by the automated software. At the time, one European country (Denmark?) was already using the automated software and there was a good bit of criticism of the TSA for not using it as well. The software available at that time had a false-positive rate higher than the TSA would accept so they set them up with operators. Eventually, improved software lowered the false-positive rate and all MMW scanners have now been upgraded and the remote operators removed. I don't know which software was in use in the tests references by the article.

Your argument sounds like Clinton saying that the answer depends on what the definition of the word "is" is.

The AIT will alarm from concealed explosives. That meets the definition for detection.

de·tect/diˈtekt/
Verb: Discover or identify the presence or existence of.

By your definition the AITs, x-ray, and CTX scanners don't detect anything at all because none of them ever identify the substance that triggers an alarm. That would leave us with the WTMD and hand-searches of all carry-on and checked luggage.

There are no 100% foolproof security measures. There never will be. The doors are a big improvement over what we had before but only a fool would think that they make it impossible for a group of hijackers to take control of the airplane.

They do. You must always have two people in the cockpit in flight so that one can view the person requesting access through the peep-hole before the door is unlocked.

Wouldn't be hard for one pilot to overpower the other, though. The crash axe, which is required to be in each cockpit, would make it a rather lopsided battle.