THE SEARCH FOR THE MISSING PLANE

International search teams comprising 42 ships and 39 aircraft are combing the sea to the east and west of the Malaysian mainland.

The teams have hundreds of square miles to cover and little information to go on. There have been conflicting reports about the last known location of the Boeing 777 passenger jet.

No confirmed wreckage has been found and tests showed that two oil slicks in the South China Sea were not related to the aircraft, officials said.

Early search efforts focussed on waters between Malaysia and Vietnam, off Malaysia's east coast.

On Tuesday, Malaysia Airlines said the scope of the search had been expanded to the Malacca Strait off Malaysia's west coast, and the land between the two coasts, amid reports that the plane could have turned back.

On Wednesday, the search was extended to the Andaman Sea, north of the Malacca Strait.

As well as possible sightings of wreckage, the search teams will be trying to find the aircraft's emergency locator transmitter (ELT) which is a location beacon.

However aviation experts say ELTs do not always work in the event of a major crash into water.

The plane also has a "black box" consisting of the cockpit voice recorder and the flight data recorder.

If immersed in water it should activate a "pinger" that can draw investigators to the location, although the signal cannot be detected over long distances.

Malaysia has deployed around 18 aircraft and 27 ships, including the submarine support vessel MV Mega Bakti which is able to detect objects in water at depths of up to 1,000m.

Huge numbers of maritime police, air force and other personnel are also taking part in the hunt.

China, Vietnam, USA, Thailand, Australia, Singapore, Indonesia, New Zealand, Japan and the Philippines are also contributing ships, aircraft and personnel, while other nations such as India and Brunei have also offered support.

The majority of the 239 people on board flight MH370 were Chinese, and Beijing has dispatched nine warships to help in the search and rescue mission.

First to be sent was the frigate Mianyang which was diverted to the south-east of Vietnam. It was joined by the landing craft Jinggangshan and its support vessels.

Destroyer Haikou and amphibious landing ship Kunlunshan set off on Sunday from two southern Chinese ports with a 50-strong marine corps as well as assault boats and rubber dinghies aboard, according to the People's Liberation Army ( PLA) Navy.

On Tuesday, China said it also deployed two military aircraft, and up to 10 satellites, to assist the search.

Vietnam has set up command posts at Phu Quoc island - the closest port to the plane's last known location - and Ca Mau airport on the country's southern tip.

It has dispatched at least eight ships and seven aircraft to the search.

The BBC's Nga Pham said personnel from the navy, air force and coastguard had been mobilised.

"The commitment from the Vietnamese authorities is very big but their problem is the lack of resources and modern equipment," she said.

"The airplanes are very old, they are Soviet-made, they are not equipped to do sophisticated and long-haul investigation."

The United States has deployed two navy ships, the USS Pinckney and Kidd from the Seventh Fleet, which had been on training and security operations in the South China Sea.

The Arleigh Burke-class destroyers carry MH60 Seahawk helicopters, which can operate missions lasting more than 10 hours at a time and cover a range of 245 nautical miles.

They have been flying at night over the Gulf of Thailand using Forward Looking Infra-red (FLIR) cameras.

A US P-3C Orion aircraft, normally based in Okinawa, Japan is also on the scene, bringing long-range surveillance capabilities.

Commander William Marks from the US Seventh Fleet said the P-3's search equipment was highly sensitive.

"Just from the air we can see things as small as almost the size of your hand, or a basketball. So it's not a matter of if we can see it - it's an extremely large area," he told the BBC.

"They [flight recorders] typically have a radio beacon and so for example our P-3 - if they are flying within a certain range of that - will pick up that radio beacon."

The P-3 can cover more than 1,500 square miles every hour (about 4,000 square kilometres).

The US's National Transportation Safety Board has also sent a team to Asia, in case assistance with the investigation is required.

Australia and New Zealand have sent a total of three P-3C Orion aircraft to join the search for the missing aircraft, which had six Australians and two New Zealanders on board.

Singapore has sent two warships, a submarine support and rescue vessel, a Sikorsky naval helicopter and a C-130 aircraft.

The submarine has divers on board who can help search for clues underwater, the Ministry of Defence said.

Indonesia has dispatched a corvette, four rapid patrol vessels and a maritime surveillance plane after Malaysia requested assistance to scour the waters around Penang Island in the Malacca Strait.

The Thai Navy has dispatched a Super Lynx helicopter and a patrol ship to the Andaman Sea, west of Thailand.

It has also put two other ships on standby in the Gulf of Thailand, awaiting a request for assistance from Malaysia.

The Philippines has dispatched a Fokker F-27 and an Islander plane and two patrol ships.

It has also placed on alert a Hamilton-class cutter vessel and a C-130 plane to join in the mission, if needed.

Japan has sent up to four military aircraft to assist the search.

India says Malaysia has requested assistance in its search in the Andaman Sea, and that the two countries are discussing the specific assistance required.