Please please dont compare air to rail.
I teach train drivers....Uk rail is a single driver operation. If anything happens to the driver....the train stops; there is sufficient protection built into signalling systems to maintain train separation.
Lets be honest, we are not far away from ground controllers 'tapping' into an aircraft to bring it back home if pilot incapacitation occurs, but as previous posters have mentioned there are way too many variables up there!!
