Im not sure either way if installing fortress like flight deck doors is the way forward here.
I would have thought a better idea would be to have a number (possibly as a ratio to seats fitted or passengers booked) of armed security personnel on board every flight as a deterrent and means of counter action to any terrorist threat. This would also solve the problem of air rage at a stroke.
As to who should pay for this, everyone should ie the tax payer. This type of terrorism is not just the airline's problem but everyone's problem to an equal extent. Its quite conceivable that there were people in the WTC who had never boarded an aircraft but suffered just as much as the poor passengers on board those aircraft.
[ 12 September 2001: Message edited by: GearUp CheerUp ]