For better or for worse the hi-jack as we know it will no longer work because all the other passengers on the aircraft know that they are dead people unless they take the hi-jackers on and win.
It did not take the brave people on the 9/11 aircraft that was prevented from hitting the terrorists target to catch on to the realitys of the situation and act.
The flight crews will no longer open the flight deck door what ever is going on in the cabin.
For these reasons I think that any attempt at hi-jack will result in the passengers "overpowering "the terrorists and the flight crew keeping control of the aircraft.
The political terrorist is quite new to the American people and the events of 9/11 have shocked the American people to the core but in europe this terrorist activity has been a fact of life for years and so while keeping alert for terrorist actions we do not see the odd knife (or boxcutter as you call them ) as a threat in its self , after all every mechanics tool box has one and in an aviation industry as big as the one in the USA one or two boxcutters are bound to go missing by accident from time to time.
If you Americans dont cool down this hysterical reaction to small every day events then the American way of life will be destroyed and the terrorists will have won.