I vote against.

We are fighting the last battle with this one.

I don't feel comfortable with a firearm on the plane, especially in the cockpit. Why not have tazers, and bullet proof cockpits and doors, and give them a big hammer in the cockpit. That'll stop most any attack.

A gun is not going to be of much help, especially if a terrorist has a grenade, or has a gun and threatens to execute a passenger every minute unless the pilots give up.