Can you remember when lifts had operators? The Green Man can, but only just. They were on the way out when The Green Man was a boy, replaced by the more cost effective self operated models. You press a button and the lift looks after closing the doors, finding the correct floor etc.

We think nothing of it these days but when they first came people must have been pretty anxious about getting into a lift without an operator. Do you think that it was silly of them? That's probably how people will feel 50 years hence when the matter of flying in a pilotless plane is concerned.

Pilotless planes have been operating for sometime, particularly in dangerous situations. Unmanned Aerial Vehicles, or UAVs, as they are known are commonplace in the military these days with the role of "fighter pilot" rapidly approaching obsolescence. They were used in Kosovo, Afghanistan and Iraq very successfully for bombing raids.

Australia is planning to buy drones to monitor it’s borders for illegal immigration and drug smuggling. Other nations are exploring the possibility of using drones to monitor the seas for both piracy and storms.

Northrop Grumman have taken a further step with their UAV the Global Hawk, pictured. It it is the first UAV to get approval to fly in civilian airspace. The next step is a pilotless passenger aircraft but public apprehension may mean this is a long way off yet.

Visit NASA's UAV website here.