You're trying to fix a problem that no longer exists, and in the process of doing so you'd actually be creating the problem that you want to defend yourself against! Your "cure" is infinitely worse than the disease!
The best weapon the 9/11 hijcakers (who, in case you haven't heard, didn't use guns) had at their disposal was the naivete of their victims. We are no longer that naive. If a hijacker or group of hijackers attempted to seize control of a plane with boxcutters or the like, they'd be beaten down in rather short order. And a boxcutter or small shank is about the best weapon that a potential hijacker could realistically get aboard a plane with under todays security screening system. That same group armed with guns (guns that you and others have let them on the plane with) is going to be an entirely different story. Having a CCW doesn't change somebody into a saint, nor do you have to be Mother Teresa to get a permit. The only one being naive is you and your wishful thinking that it's easy as pie to identify and separate the good guys from the bad guys, to say nothing of the insane delusions that some wannabe sky marshals on this site have about being able to whip out a pistol and in the blink of an eye and take out 3 or 4 BGs without spilling their coffee (BGs that were allowed on the plane in the first place because of their utterly laughable "plan" to improve airline safety!). Yeah....let's give every nut case, radical, fanatic, and terror cell a good chance at getting aboard a plane with guns. That way we can unleash our inner Rambos instead of having to just sit there and read the airline magazine. What a great idea.
This whole thread reeks of the ego and vanity of certain people and smacks of some major league sheepdoggy-ness.