Let's be clear, my dad and I disagree on a lot of things[1]. I do not advocate passenger hostile systems in airplanes.

The interesting thing for me, reading the comments is that my actual comment (that if security costs 10x to defend and 1x to perpetrate, then the system will by definition fail) has no feedback. I think about ways to "even" the cost on these things. Biometric security is one (although it too has its issues). Using something like Clear[2] at an air port to insure people are who they say they are, and having vetted that person via other mechanisms prior to their flight, seems more efficient and harder to subvert than the current system. It converts the problem from "150 unknown actors are getting on a plane" to "150 known actors are getting on a plane." Does it make it difficult enough for the attackers? They have to forge biometrics and disguise the actual flight they are taking. Not sure if it completely levels the field but it raises the cost for the attacker.

[1] He also thinks that every state should allow and encourage people to carry hand guns so that "crooks and crazy people would think twice."

[2] See http://clearme.com basically at signup biometrics and other data are used to confirm identity and to take a picture. When you arrive at the airport your boarding pass is scanned (an presumably validated) and the operator gets a picture of what you should look like given your biometrics. So if you steal someone else's fingerprints you don't look like them.