These strange-looking planes carry a wealth of sensors in their bulbous noses: colour and black-and-white TV cameras, image intensifiers, radar, infra-red imaging for low-light conditions and lasers for targeting. They can also be armed with laser-guided missiles.
Each multi-million dollar Predator or Reaper system comprises four aircraft, a ground control station and a satellite link.
Although drones are unmanned, they are not unpiloted - trained crew at base steer the craft, analyse the images which the cameras send back and act on what they see