The Sriwijaya Air passenger plane lost contact after taking off from Indonesian capital Jakarta earlier today en route to Pontianak in West Kalimantan province.
It's been reported the flight fell 10,000ft in less than one minute, about four minutes after taking off.
It had more than 50 people on board.
Flightradar24 tweeted: "We are following reports of a missing Boeing 737-500 in Indonesia. We hope to have more information soon."
The flight monitoring website later added: "Sriwijaya Air flight #SJ182 lost more than 10,000 feet of altitude in less than one minute, about 4 minutes after departure from Jakarta."
Sriwijaya Air said in a statement it is still gathering more detailed information regarding the flight before it can make any statement.
According to CNBC Indonesia, the flight vanished at 2.40pm local time, moments after taking off from Soekarno-Hatta airport.
The Sriwijaya Air plane lost contact around Lancang Island, Thousand Islands, the manager of branch communication and legal at Soekarno-Hatta Airport, Haerul Anwar, said.
The Indonesian Transport Ministry spokesperson, Adita Irawati, confirmed that there had been a loss of contact with the Sriwijaya Air aircraft, reports CNBC Indonesia.
"We are currently under investigation and coordinated with Basarnas and the National Transportation Accident Committee (KNKT)," said Adita.
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