I hope those science engineers had figured out the motives of Al Queda for taking control of one of these unmanned planes.
and continuing with concerns about someone getting remote access to the airplane and using it for mischief. Now that is one thing I'm not to concerned about. For one, the flight program on an unmanned airliner would be one of the most carefully designed programs ever written. If you can count on anything, ti would be that it can't be overridden remotely. As for other attacks, in this day and age, if you can access the avionics software of a plain, I'll bet you can lockout all the cockpit controls and fly it into whatever you want so I don't think there is any more risk cropping up here than we have right now. Frankly, I suspect physical takeover of a maned plane is more likely.