I'm with Chimbu Chuckles. The simplest quickest solution, that would assauage passengers' and crews' immediate fears is the immediate introduction of ingognito air marshals, at least one per flight. A flight deck is not a terribly difficult place to defend, a very confined space, with only one useable narrow access. Assuming the would be attacker doesn't have a gun, then a/c on aotopilot and an electric cattle prod would do the trick.
Seriously though, all solutions have to considered. What is true is that every airline and authority is going to have to address crew training. In spite of the fact that aircraft have frequently been placed in danger by disruptive pax, there has not been to my knowledge any serious airline reaction except "jail 'em". Too late.
