It is a version of the C-130 Hercules transport aircraft and flies at less than 300mph (482 kph). But with a range of approximately 2,000 miles (3,200 kilometres) it can loiter over a combat area for some time without needing to refuel.

The latest model, known as Spooky II, has three large guns projecting from the left side of the fuselage: a 25mm Gatling gun that can fire up to 1,800 rounds per minute, and 40mm and 105mm cannons.

The aircraft uses video images, infra-red and radar sensors to locate targets at day and night. Its computers are designed to follow two targets with two different sensors and fire two different guns at the same time.

Former crew members say that, in practice, the guns are never fired simultaneously, partly because of ammunition considerations.

Although regarded as a successful weapon, the aircraft's slow speed makes it vulnerable. It therefore comes armed with counter-measures including chaff, flares and heat shields to mask the engines.