More of a UAV Cargo Ship than a drone. Even so, it's still a challenging piece of technology to manage remotely for such a myriad of complex systems. It begs the question of how it might increase or decrease piracy if there are no humans on-board - or how stowaways would be handled if remotely detected.
http://unbonmotgroundswell.blogspot.com/2014/02/rolls-royce-is-developing-drone-cargo.html