I don't see why the US would bother with a rescue mission, there's what, 3 Americans on board? If there was a stolen nuke (which it's doubtful Pakistan would be giving one up to terrorists, if they were in that business you'd imagine they would have already given one to the Taliban or Al Qaeda) put on board, with hostages as a deterrent, I would guess 10 out of 10 countries would still blow that thing out of the air. The radiation may be more widely dispersed, but it wouldn't be as concentrated, and the damage compared to if it were to hit the ground would be far less. Better to kill off the 230 something people, than thousands. That seems more like the plot of an action movie than what we have here.