Ahlfors, in my opinion non-metal knives are *the* security issue in this crash, and the most serious security issue out there right now. As we all know the 911 callers said that the attackers had non-metal knives, something that is very easy to get hold of. (Kevlar is used to make knives nowadays too).
Probably airports are going to have to install those "body scan" machines that were invented a couple of years ago. They use a very mild X-ray to "undress" the passenger and see what all is in their pockets and in their body. A plastic knife or a case holding it would show up on this scan. That's the *one* mechanical security measure I know of that would take care of this fatal gap in airport security.
Airports balked at installing them because of privacy concerns about airport employees putting the digital images of pax' bodies on the Net. I can't imagine these machines being hooked up to the Net.
But airports are going to have to install them now, I think. And if anyone wants my body scan, I'll recommend them to a good eye doctor for glasses. :+P
Need a new airline paint scheme? Better call Saul! (Bass that is)