Nothing is perfect. You gotta play the odds my man. One rag might defeat the system and do his evil deed by posing as a pilot. Odds are, however, that an armed American pilot would take out the next rag who attempts evil. Many more American pilots so the odds favor good vs evil.
The only thing standing between us and another hijacking is commited PASSENGERS. (Unless you count the F-16 orders.) So far, every idiot that has tried has been subdued, though unfortunately not killed, by the passengers.
I can not believe the resistance to a very simple concept: The pilot and co-pilot have guns. You risk safe conduct of the flight, they will kill you. Currently, unarmed pilots depend on unarmed passengers to control things. Nobody in their right mind thinks the TSA is protecting them from anything!
People on the ground are a little protected by the possibility an F-16 will be in range and can shoot down a hijacked aircraft and that it will crash in an unpopulated area. RIGHT! What morons!!! Only thing being protected is politicians asses, and with no regard for the rest of the population.
We remain frighteningly vulnerable. We are marking time until the other shoe drops and doing damn little to prevent it.