IMO the single step that would make the most significant change in future such attempts would be to treat all hijackings as acts of war.
The current policy is one of placating the hijacker and minimizing on-flight casualties.
The implications of the current incidents are that a hijacking be treated as an act of war, and a clear and present danger to civilian, industrial, military, and government sites. The objectives of flight crews and/or passengers must be to neutralize the hijackers. If this cannot be accomplished, the flight must be diverted. If this cannot be done, it must be destroyed.
It's not a happy picture.
Peace.