Don't get me wrong, I'm all in favour of civilian planes being taken out if that limits the damage. But that and in-flight shoot-outs with the air marshalls (who could be people with hostile intent anyway - even just loonies like the guy in Switzerland today) both seem to be tackling the problem one step too late. Best to keep the wrong sorts, and their means of doing damage, off the planes in the first place. In my view any loaded gun on board, in anyone's hands, is only going to increase the risks to all.