Trains are operating throughout some of our world's cities now without drivers on board.
Planning is currently underway in the USA to allow UAVs to operate in controlled airspace.
Please check out Global Hawk on the net.
It's similar in external dimensions (wingspan) to a B737 and succesfully flew from California to Australia and returned with it's flight profile fully automated and also without crew on board.
The 'Soviet Union' successfully flew the Buran Shuttle for several orbits without crew. At one time the USA were thinking of flying the Shuttle without crew. It's highly probable that the next generation of reusable launch vehicles will be unmanned.
The elimination of pilots (human factors) from the front of the craft will increase safety. Also a great weight savings as cockpits weigh quite a lot.
Unmanned transport aircraft will be in the future of aviation.