An AirAsia flight travelling from the Indonesia to Singapore has lost contact with air traffic control with 162 people on board.
Flight QZ8501 lost contact at 07:24 (23:24 GMT), Malaysia-based AirAsia tweeted.
Search and rescue operations are under way.
Malaysia's national carrier Malaysia Airlines has suffered two disasters this year - flights MH370 and MH17 - but AirAsia has never lost a plane.
Flight MH370 disappeared on a flight from Kuala Lumpur to Beijing in March with 239 passengers and crew, and MH17 was shot down over Ukraine in July, killing all 298 on board.
The AirAsia flight had been due to arrive in Singapore at 08:30 (00:30GMT).
The missing jet had requested a "deviation" from the flight path due to bad weather, the company said.

The flight arrivals board at Changi Airport in Singapore, where the AirAsia flight was due
There were 155 passengers on board, with 138 adults, 16 children and one infant, the company said in a statement. Also on board were two pilots and five cabin crew.
Most of those on board were Indonesian, but there were six others on board, AirAsia has said: three South Koreans, and one each from France, Malaysia and Singapore.