Of course that's assuming the terrorists wouldn't have heard of gas masks... If they had the gas it might even make their job easier.

Technical fixes have a very limited role I would think. Worth introducing some of them, but they just reduce danger, not eliminate it.

One suggestion I've seen they are working on is having a facility to override the pilot's controls and take over by remote control. Which opens the nightmare prospect of having the remote control centre taken over, and hundreds of planes guided to disaster.

Simplest and most effective, if possibly unpopular, thing to do would be one I've suggested elsewhere - make everyone hand in all their clothes and belongings prior to a flight, and give passengers some kind of pyjamas or overalls for the duration.

If I was in America I think I'd be buying shares in railway companies.