Why just one firearm on the plane? Why not arm the cockpit and have random numbers of "Sky Marshals"? It would certainly make airplanes a less attractive target if the Terrorists did not know what they would encounter. But if terrorism were to step up a level or two they would take that risk too. In all honesty the only way to prevent these attacks is to ensure that these groups cease to exist. After eleven years in Naval Special Warfare during the Reagan/Bush years this is the only solution that offers a high probability of success.
