Jakarta - Pilots aboard a missing AirAsia aircraft carrying 162 people had requested a deviation from the plane's flight plan due to bad weather shortly before losing communication with air traffic control, an AirAsia statement said.
The pilots requested "deviation due to en route weather before communication with the aircraft was lost while it was still under the control of the Indonesian Air Traffic Control [ATC]", AirAsia said in a statement on its Facebook page.
The aircraft was en route from Indonesia to Singapore on Sunday morning before losing communications with the airline, in the third crisis for a Malaysian carrier this year.
Air traffic controllers lost contact with the Airbus A320-200 around an hour after it left Juanda international airport in Surabaya in east Java at 5:20am. It was scheduled to arrive in Singapore at 08:30.
The airline said 156 of those on the flight were Indonesians, along with three South Koreans and one person each from Singapore, Malaysia and France also missing.
On board were 138 adult passengers, 16 children and an infant, in addition to the two pilots and five cabin crew.
Search under way
The Indonesian air force said two of its planes had been dispatched to scour an area of the Java Sea, southwest of Pangkalan Bun in Kalimantan province.
"The weather is cloudy and the area is surrounded by sea. We are still on our way so we won't make an assumption on what happened to the plane," said Indonesian air force spokesperson Hadi Cahyanto.
The aircraft was operated by AirAsia Indonesia, a unit of Malaysian-based AirAsia which dominates Southeast Asia's booming low cost airline market.
An official from Indonesia's transport ministry said the pilot asked to ascend 6 000 feet to 38 000 feet to avoid heavy clouds.
"The plane is in good condition but the weather is not so good," Djoko Murjatmodjo told a press conference at Jakarta's airport, addressing reports of severe storms in the area where the jet went missing.
Murjatmodjo said search efforts were being focused on an area between Belitung island and Kalimantan, on the western side of the island of Borneo, about halfway along the expected route of Flight QZ8501.
Singapore has offered help from its navy and air force in the hunt for the plane.
US briefed
The White House said US President Barack Obama had been briefed on the disappearance and that it was monitoring the situation.
Indonesia, a vast archipelago with poor land transport infrastructure, has seen an explosive growth of low-cost air travel over recent years.
But the air industry has been blighted by poor safety standards in an area that also experiences extreme weather - although AirAsia said the missing jet last underwent maintenance on 16 November.
The company swiftly replaced its bright red logo to a grey background on its social media pages.
The plane's disappearance comes at the end of a disastrous year for Malaysian aviation.
Malaysia Airlines Flight MH370, carrying 239 people, vanished in March after inexplicably diverting from its Kuala Lumpur-Beijing course. No trace of the aircraft has been found.
Just months later another Malaysia Airlines plane went down in July in rebellion-torn eastern Ukraine - believed to have been hit by a surface-to-air missile - killing all 298 aboard.
Support
Malaysia Airlines posted a message of support to AirAsia on its Twitter page, saying, "Our thoughts and prayers are with all family and friends of those on board QZ8501", along with the hashtag "stay strong".
AirAsia, Asia's budget travel leader, is led by flamboyant boss Tony Fernandes, a former record industry executive who acquired the then-failing airline in 2001.
It has seen spectacular success and aggressive growth under his low-cost, low-overhead model.
While its rival Malaysia Airlines faces potential collapse after two disasters this year, AirAsia confirmed this month its order of 55 A330-900neo passenger planes at a list price of $15bn.
