The aircraft is a 27-year-old Boeing 737-500, according to registration details included in the tracking data.
A spokesman for the search and rescue agency, Yusuf Latif, said it had not been confirmed how many people were on board. Local Metro TV reported the plane was carrying 56 passengers, along with two pilots and four cabin crew.
Latif said search and rescue teams were on their way to search for the plane at Thousand Islands in the Java sea.
The teams would scour the area. The flight’s status would be upgraded to “missing” if the preliminary search was inconclusive, Latif said.
Reliable tracking service FlightRadar24 has reported that the plane lost more than 3000 metres in altitude in less than one minute, about four minutes after departure from Jakarta.
Sriwijaya Air said in a statement it would gather detailed information about the flight before releasing further information.
Sriwijaya Air was founded in 2003 and is Indonesia’s third-largest airline. It carries more than one million passengers each month to mainly Indonesian destinations, but also offers international flights across Asia, including to China, Malaysia and Singapore.
More to come.