I don't understand..
EVERYTHING gets scanned. Your suitcase may be searched more thoroughly at the TSA's leisure, but your carry on luggage is always opened up and anything electronic scrutinized right in front of you where you have to answer for it. A lot of modern devices including most 'ultrabook' laptops have non-removable batteries. Now they're going to fly in the cargo hold where if something happens it may not be apparent until there's a catastrophe? Unless all luggage is going on a separate cargo plane, what exactly is this accomplishing?
Do they think someone is going to launch a cyber attack against the plane's avionics? If so, how could this not be accomplished every bit as easy from a modded cell phone?