Earlier quoted context omitted.
Ceramic, glass and plastic knives can be extremely dangerous and yet they probably don't show up on these machines at all. The utility of these machines is questionable to say the least. Bruce Schneier observed, like you did, that the heavily secured cockpit door is one of the only real improvements made to airplane security in the last few decades.
> and yet they probably don't show up on these machines at all Uh, yeah, they do. Have read anything about backscatter xray machines? The real way to defeat these machines is to hide things in folds of your flesh. It can see through clothes, but not too much skin. In staged demonstrations, fat people have gotten a metal pistol through, no problem.
Quick examples: https://www.wired.com/2014/08/study-shows-how-easily-weapons...
A gun(!) is basically invisible in the scan. Is teflon tape enough to defeat these stupid machines?