No distress call is reported to have been issued by the crew of the missing AirAsia flight QZ8501, officials report.
The aircraft was flying from Indonesia to Singapore with 162 people on board when it lost contact with air traffic control.
Flight QZ8501, an Airbus 320-200, went missing at 07:24, Malaysia-based AirAsia tweeted.
Indonesian military planes are searching an area of the Java Sea.
AirAsia, a budget airline, has never lost a plane, but Malaysia’s national carrier Malaysia Airlines has suffered two this year – flights MH370 and MH17.
It left the Indonesian city of Surabaya in eastern Java at 05:20 local time and was due to arrive in Singapore at 08:30.
The missing jet had requested a “deviation” from the flight path due to bad weather, the company said.
Indonesia’s transport ministry said the pilot had asked permission to climb to 38,000 ft (11,000m) to avoid thick cloud. No distress call is reported to have been issued by the crew.
AirAsia Indonesia is an affiliate of the Malaysian company AirAsia, operating domestic flights round the Indonesian archipelago as well as international services to Malaysia, Singapore, Australia and Thailand.
AirAsia Indonesia was banned from flying to the EU in 2007 due to safety concerns but this was lifted in July 2010.
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