Come on... if this was really a “foreseeable risk” it wouldn't have happened.
Now today it might be concidered a “foreseeable risk”, but what can the airlines really do about it? They've beefed up screening and security measures, but if some crazed terrorist group tried hard enough, there is no doubt in my mind that they could pull it off again. There will always be moments of insecurity or someone not paying attention, and a moment is all they need.