An Indonesian flight carrying more than 50 passengers has lost contact within four minutes after taking off from Jakarta, according to flight tracker website FlightRadar24.
Sriwijaya Air flight #SJ182 had been flying to Pontianak in Borneo, Indonesia, around 740km from Soekarno-Hatta Airport.
The Boeing 737-500 lost more than 10,000ft of altitude in under a minute and an ADS-B signal was lost at 2.37 p.m local time.
The 27-year-old plane was a Boeing 737-500, which is not the same as the controversial Boeing 737 Max model involved in two major crashes in recent years.
Sriwijaya Air said in a statement it was still gathering more detailed information about the flight.