The events of the last few weeks prove that terrorists could care less about airplanes in the grand scheme of things... They will inflict damage on soft targets. At one point you could consider the lax security on US aircraft a "soft targer" (e.g. I'm more concerned on un-reinforced cockpit doors than the search for pointy objects).... however they will move onto what is considered a target with a higher rate of success - commercial aircraft isn't it today.