“It is not an easy operation in the sea, especially in bad weather like this,” he said.

Indonesian Air Force spokesman Hadi Tjahjanto said the search was now focused on a patch of oil spotted off Belitung island in the Java Sea.

An Indonesian official said earlier on Monday that objects had been spotted in the sea by an Australian search plane hunting for the plane, which vanished with 162 people on board.

Jakarta’s Air Force base commander Rear Marshal Dwi Putranto said he was informed that an Australian Orion aircraft had detected suspicious objects near Nangka island, about 100 miles southwest of Pangkalan Bun, near central Kalimantan, or 700 miles from where the plane lost contact.

An Indonesian helicopter also spotted two pools of oil near the search area.

Shares in the company on Monday closed down 8.5 per cent.

Indonesia’s National Search and Rescue Agency chief Bambang Soelistyo said at a press conference on Monday morning: "Based on the coordinates given to us and evaluation that the estimated crash position is in the sea, the hypothesis is the plane is at the bottom of  the sea.

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“That’s the preliminary suspicion and it can develop based on the evaluation of the result of our search.”

Shocked family members huddled at Surabaya airport, in Indonesia's second largest city, from where the Airbus A320 took off yesterday morning, awaiting news of the plane, operated by an airline whose parent company is based in Malaysia.

It is the third incident involving Malaysian jets this year: Malaysia Airlines suffered two tragedies - Flight MH370, with 239 people on board, vanished in March; Flight MH17 was shot down over Ukraine in July, killing all 298 people aboard.

Indonesia and Singapore launched a search-and-rescue operation for Flight QZ8501 yesterday near Belitung island, in the Java Sea, in the area where the plane lost contact with air traffic control, about 42 minutes after taking off. The search was halted at 7pm because of darkness and bad weather, but it is due to resume this morning.

The flight had travelled a little less than half of its journey to Singapore when it disappeared from radar systems.

There were no Chinese nationals on board, but the Chinese foreign ministry said it was watching the developments. Spokeswoman Hua Chunying said the government was deeply concerned about the people onboard and extended her sympathy to their families.

Bian Liangwei, whose brother was on Flight MH370, which remains missing after taking off on March 8, said: "I hope all the people aboard the AirAsia flight are fine."

Speaking 10 hours after the plane lost contact, Indonesian Vice-President Jusuf Kalla expressed his deep concern. "It is most possible that it has experienced an accident," he said.

The last communication between the pilot and air traffic control was at 7.24am, AirAsia said. The plane, which took off at 5.35am, had been due to land at 8.30am.

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Djoko Murjatmodjo, Indonesia's acting director general of transportation, said there had been no distress signal from the cockpit of the twin-engine, single-aisle aircraft. "We hope we can find the location of the plane as soon as possible, and hope that God will give us guidance to find it," he said.

AirAsia said the plane was on the submitted flight plan route. But it had requested a deviation to the left and also to climb to 10,360 metres owing to bad weather before communication with the aircraft was lost while it was still under the control of Indonesian Air Traffic Control.

"This is my worst nightmare," AirAsia founder Tony Fernandes tweeted.

Sunardi, a weather forecaster at the Indonesia's Meteorology and Geophysics Agency, said dense storm clouds were detected at up to 13,400 metres in the same area at the time the plane was reported to have lost contact.

"There could have been turbulence, lightning and vertical as well as horizontal strong winds within such clouds," Sunardi, who like many Indonesians uses only one name, said.

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The plane had an Indonesian captain, French co-pilot, five cabin staff and 155 passengers, including 16 children and one infant, AirAsia said.

Among the passengers were three South Koreans and one each from Singapore, Malaysia and Britain. The rest were Indonesians.

Transport Minister Ignasius Jonan said search-and-rescue efforts involved Indonesia's army and the national Search and Rescue Agency, as well as rescuers from Singapore and Malaysia. Two hundred rescuers were sent to the area, including three aircraft.

Malaysian Prime Minister Najib Razak, expressed solidarity with AirAsia. In a tweet he said: "Very sad to hear that AirAsia Indonesia QZ8501 is missing. My thoughts are with the families. Malaysia stands ready to help."

US President Barack Obama, on holiday in Hawaii, was briefed about the jet's disappearance, the White House said.

Sunardi, a forecaster at Indonesia’s Meteorology and Geophysics Agency, said dense storm clouds were detected up to 13,400 meters (44,000 feet) in the area at the time.

“There could have been turbulence, lightning and vertical as well as horizontal strong winds within such clouds,” said Sunardi, who like many Indonesians uses only one name.

Airline pilots routinely fly around thunderstorms, said John Cox, a former accident investigator. Using on-board radar, flight crews can typically see a storm forming from more than 100 miles away.

In such cases, pilots have plenty of time to find a way around the storm cluster or look for gaps to fly through, he said.

“It’s not like you have to make an instantaneous decision,” Cox said. Storms can be hundreds of miles long, but “because a jet moves at 8 miles a minute, if you to go 100 miles out of your way, it’s not a problem.”

Associated Press and Agence France Presse