The problem of fully automated, unmanned airplanes is the actual probability of a malfunction or number of malfunctions occurring so that the result is a catastrophic accident.
The calculated, estimated or inferred probability is not the actual probability.
The engineers work with complex mathematical reasoning. But no matter how complex and advanced a mathematical calculation is, it only works really well if the data it is based on is the truth, all the truth and nothing but the truth.
The orders of magnitude they are working with are almost unconceivable. Same as economy, I dare to say. So many experts, nobel prizes, etc... They don't know a shi*t of what is going to happen. They can only explain (more or less, and who knows if they are right...) what happened already.
World's economy has to deal with the "black swan". I don't think it is advisable to make aviation deal with it (even more that right now, I mean).
I am convinced that automation safety is greatly increased if there is a human in the cockpit, or vice versa. And even more if there are two humans, since two humans provide more than twice as much safety.