There are various forms of the H-53, but the MH-53J and M Pave Low are low-level, long-range versions designed to get into enemy areas undetected, day or night or in poor weather, to drop, pick up, or re-supply special forces.

It is equipped with terrain-following and terrain-avoidance radar, an infra-red sensor and GPS satellite navigation.

The latest M version produces a digital 3D perspective of the surrounding terrain which provides the pilots with information on flight route, man-made hazards such as power lines and even distant enemy threats. It creates this display by downloading data from US military satellites.

The helicopter is armour-plated in critical areas and carries three machine guns. It can transport 38 troops in addition to the six crew.

It has a huge, six-blade rotor. When turning this gives the aircraft an overall length of about 100 feet (30 metres).

It can fly at 160 mph (265 kph) and has a range of more than 600 miles (966 km) but can refuel in flight.

The US Air Force currently flies 38 Pave Low helicopters with its 20th and 21st special operations squadrons based at Hurlburt Field, Florida and at RAF Mildenhall, England.