Air marshalls have considerable training on weapon retention--far more (I would hope) than most CCW carriers. In addition, they also have the authority, once they have revealed themselves--to demand that everyone else remain outside of grabbing distance (IIRC there was a bit of a stink awhile ago because an air marshall who reacted to a crazed passenger did precisely that for the duration of the flight). Ordinary citizens with CCWs would not have the authority to forbid other people from getting close enough to grab their weapons, and lacking such authority could not reasonably keep their weapons safe.
BTW, while sky marshalls may be a useful adjunct to arming pilots, the armed pilots should be the most important component of flight security.
Seems this would create a real sight picture problem, panic in the cabin, aircraft trim adjustment needed, and great potential for the bad guys to nab hostages.
We know what the score is, keep control of the plane in the proper hands or die. Either by the terrorist's hands or by one of our own missiles.
Give the pilots the means to defend the cockpit, surely. But if you want me to get on an aircraft, you will not deny me the means to defend myself, even a pocket knife would help.
In the meantime, there is noplace I need to go I can't drive and at least retain an item which can be used as an expedient weapon. (Large Crescent wrench, pipe wrench or the like).
I can drive 700 miles west, 400 miles east, 70 miles north, or over 200 south and carry a pistol concealed the whole way, legally. I don't need a plane and refuse to place my safety solely in the hands of one other person who may be outnumbered, out gunned, or simply 'made' and neutralized by people who have shown a predilection toward doing their research.
Like the pilots, who already have control over life and death, many CCW holders would gratefully accept the additional training and responsibility, in exchange for full faith and credit under the Constitution for their licenses.
Crossing a state border does not turn me into a homicidal maniac, regardless of altitude.