It tickles me all this talk of "it will land at the nearest suitable airport" The point is how it will handle the combination of Wx, unserviceable equipment on the ground and on the AC, traffic overload, company interests, pax convenience... How much would it cost to fit all these airports to be able to accept an unmaned AC at short notice (or no notice). If the signal is jammed presumably all the AC in that airspace will suddenly be heading independently to their "nearest suitable airport" how and who would sort out the ensuing traffic caos.
Towards the beggining of this thread somebody was told that a 777 would land in Indonesia in six more hours without further imput. This assumed that the rwy in use stays the same, there are no delays and no conflicts with other traffic, there is no adverse wx on route, the descent winds are as planed, the landing is done flaps up and gear up... the list goes on.
I remember that a few months ago there was a competition in the US where unmaned vehicles (cars and one motorbike as I recall) had to negotiate a 20mile course through the desert. Not one finished the course. Remember, they did not have to contend with Wx, traffic....they operated in 2 dimensional environment. And they did not have to be fail operational.
The crash rate of existing unmaned vehicles is phenomenal. Since they are quite rear, military and small they normally crash out of sight. How many unmaned cargo ac would need to crash into populated areas to discredit the whole concept?
It will happen in the end since time is long and who knows, time travel might happen... but not for a long, long time.