Reliable tracking service Flightradar24 said on its Twitter feed that Flight SJ182 "lost more than 10,000 feet of altitude in less than one minute, about 4 minutes after departure from Jakarta".
Surachman, a local government official, told Kompas TV that fishermen found what appeared to be the wreckage of an aircraft in waters north of Jakarta and a search was underway. Other channels showed pictures of suspected wreckage.
"We found some cables, a piece of jeans, and pieces of metal on the water," Zulkifli, a security official, told CNNIndonesia.com.
The aircraft is a 27-year-old Boeing 737-500, according to registration details included in the Flightradar24 tracking data. It took off just after 2.30 p.m. (0730 GMT) and lost contact soon afterwards, a search and rescue official told local television.
Sriwijaya Air, an Indonesian airline, said in a statement it is still gathering more detailed information regarding the flight before it can make a fuller statement. Officals did not expect survivors.
A Boeing 737 MAX operated by Indonesian airline Lion Air crashed off Jakarta in late 2018, killing all 189 passengers and crew. The plane that lost contact on Saturday is a much older model.
National search and rescue agency Basarnas said it could give no immediate comment.
© Reuters, aero.uk | Image: Sriwijaya Air | 09/01/2021 12:18