SEA King helicopters are among the most recognisable aircraft in the world and are usually associated with search and rescue operations.These distinctive craft, with their long, bright-yellow fuselage, are operated by the Royal Air Force from bases such as Wattisham, Lossiemouth in Scotland and Boulmer in Northumberland.

SEA King helicopters are among the most recognisable aircraft in the world and are usually associated with search and rescue operations.

These distinctive craft, with their long, bright-yellow fuselage, are operated by the Royal Air Force from bases such as Wattisham, Lossiemouth in Scotland and Boulmer in Northumberland.

An impressive sight flying low over Britain's coastline at speeds of up to 143mph, they have played a key role in locating missing people both on land and at sea.

But the helicopters that collided over the Gulf were Royal Navy-operated Mk7 Airborne Early Warning (AEW) Sea Kings that fulfil an entirely different role.

Following the Falklands conflict in 1982, military commanders decided that AEW, or Airborne Surveillance and Area Control (ASAC) as it is now called, was an essential part of air power at sea.

Sea Kings were chosen for the job and provide vital tactical control to the Sea Harrier "Jump Jets" and other planes based on British aircraft carriers.

Using their hi-tech radar equipment, the Sea King can detect low-flying enemy aircraft that could be about to target surface ships under conventional shipborne radar cover.

The three crew on board are made up of one pilot and two observers.

Manufactured by AgustaWestland in Britain, the Sea King was developed for the Royal Navy and has been in service for more than 25 years.

There are more than 300 in service with both the RAF and Royal Navy while they are also used by the navies and air forces of countries such as Australia, Egypt, Germany, India and Pakistan.

Other versions of the helicopter used by the Royal Navy are the Mk6 Anti-Submarine and the Mk4, which is used to support Royal Marine commandos.

The Mk6 has its own weapons, including the Sting Ray lightweight torpedo, depth charges and a 7.62mm machine gun mounted in its doorway.

Monitoring equipment include an advanced, integrated passive sonar system, a tactical navigation system and electronic support devices which detects radar transmissions from other craft.

The Mk4 acts as a workhorse and is capable of carrying up to 27 troops over a range of about 400 miles. It can also carry Land Rovers, 105mm guns and air defence missile systems.

It, too, has its own defence systems.

Anti-submarine Sea Kings are scheduled to be replaced by the Merlin, a derivative of the Anglo-Italian-produced EH101 helicopter.

The 13 Sea King AEWs have recently undergone an upgrade, equipping them with more up-to-date radar and radio systems. The first two upgraded craft were delivered last year.