QZ8501 Ships and planes resumed the search for wreckage, bodies and black boxes of a doomed AirAsia plane today after Indonesian rescuers found several bodies and debris floating in shallow waters off the coast of Borneo.

Indonesia's search-and-rescue agency had obtained a sonar image it says may be the body of the missing plane at the bottom of the Java Sea, the Wall Street Journal said.

The newspaper quoted the agency as saying the image appeared to show an aircraft upside down in 24-30 metres of water.

But waves two to three metres high and winds prevented divers from searching the crash zone for the sunken remains.

Flight QZ8501 had 162 people on board when it vanished during bad weather on Sunday, about 40 minutes into its flight from the Indonesian city of Surabaya to Singapore.

Aviation experts believe that, weather permitting, the fuselage may be easily found by divers as the aircraft probably only broke up when it hit the water.

Searchers found three bodies on Wednesday morning, including a flight attendant, bringing the total to six so far, said the head of the search and rescue agency, Fransiskus Bambang Soelistyo.

The fully clothed bodies could indicate the plane was intact when it hit the water and support a theory that the Airbus A320-200 suffered an aerodynamic stall and plunged into the sea.

"The fact that the debris appears fairly contained suggests the aircraft broke up when it hit the water, rather than in the air," said Neil Hansford, a former pilot and chairperson of consultancy firm Strategic Aviation Solutions.

Most of the people on board were Indonesians. No survivors have been found.

Indonesian President Joko Widodo ( right ) said his priority was getting bodies off the bottom of the Karimata Strait in the Java Sea, where rescuers retrieved a plane door and other debris on Tuesday, so victims could be identified.

"I feel a deep loss over this disaster and pray for the families to be given fortitude and strength," Widodo said in Surabaya yesterday after grim images of the scene in the Java Sea were broadcast on television.

AirAsia chief executive Tony Fernandes has described the crash as his "worst nightmare".

Widodo said AirAsia would pay an immediate advance of money to relatives, many of whom collapsed in grief when they saw the television pictures of debris and a body.

The United States said its destroyer USS Sampson and combat ship USS Fort Worth were awaiting instructions from the Indonesian search command on the recovery operation. Singapore said it was sending two underwater beacon detectors to try to pick up pings from the black boxes, which contain cockpit voice and flight data recorders.

About 30 ships and 21 aircraft from Indonesia, Australia, Malaysia, Singapore, South Korea and the United States have been involved in the search.

No distress call

The plane, which did not issue a distress signal, disappeared after its pilot failed to get permission to fly higher to avoid bad weather because of heavy air traffic.

It was travelling at 32,000 feet (9,753 metres) and had asked to fly at 38,000 feet. When air traffic controllers granted permission for a rise to 34,000 feet a few minutes later, they received no response from the aircraft.

Online discussion among pilots has centred on unconfirmed secondary radar data from Malaysia that suggested the aircraft was climbing at a speed of 353 knots, about 100 knots too slow, and that it might have stalled.

Investigators are focusing initially on whether the crew took too long to request permission to climb, or could have ascended on their own initiative earlier, said a source close to the inquiry, adding that poor weather could have played a part as well.

A Qantas pilot with 25 years of experience flying in the region said the discovery of the debris field relatively close to the last known radar plot of the plane pointed to an aerodynamic stall, most likely due to bad weather.

One possibility is that the plane's instruments iced up in a tropical thunderstorm, giving the pilots inaccurate readings.

The lack of a distress call indicated the pilots may have realised too late they were in trouble and were too busy struggling to control the aircraft to issue a call, the Qantas pilot said.

The Indonesian pilot, a former air force fighter pilot with 6,100 flying hours under his belt, was experienced and the plane last underwent maintenance in mid-November, said the airline, which is 49 percent owned by Malaysia-based budget carrier AirAsia.

Three airline disasters involving Malaysian-affiliated carriers in less than a year have dented confidence in the country's aviation industry and spooked travellers across the region.

Malaysian Airlines Flight MH370 went missing in March on a trip from Kuala Lumpur to Beijing with 239 passengers and crew and has not been found. On July 17, the same airline's Flight MH17 was shot down over Ukraine, killing all 298 people on board.

On board Flight QZ8501 were 155 Indonesians, three South Koreans, and one person each from Singapore, Malaysia and Britain. The co-pilot was French.

The AirAsia group, including affiliates in Thailand, the Philippines and India, had not suffered a crash since its Malaysian budget operations began in 2002.

- Reuters