An AirAsia flight travelling from the Indonesian city of Surabaya to Singapore has lost contact with air traffic control, the company has said.
Indonesian media say more than 160 people were on board the Airbus A320-200.
The aircraft, flight number QZ8501, lost contact with air traffic control at 07:24 (00:24 GMT), AirAsia tweeted.
The company said that search and rescue operations were under way for the missing plane.
An official with the transport ministry, Hadi Mustofa, told local media the plane lost contact over the Java Sea, which lies between Surabaya and Singapore.
He said the plane had asked for an unusual route before it lost contact.
AirAsia have given few other details.
"At the present time we unfortunately have no further information regarding the status of the passengers and crew members on board, but we will keep all parties informed as more information becomes available," a company statement said.