The turboprop ATR 42-500 operated by the Indonesia Air Transport was on the way from Yogyakarta to the capital city of South Sulawesi when it vanished from radar, said Endah Purnama Sari, a spokesperson for the Transportation Ministry.
The plane was last tracked at 01:17 pm in the Leang-Leang area of Maros, a mountainous district of South Sulawesi province.
Multiple search and rescue teams, supported by air force helicopters, drones and ground units have been deployed, Sari said in a statement.
“The sightings were reported to authorities and are being verified by rescue teams attempting to reach the area,” said Maj. Gen. Bangun Nawoko, the South Sulawesi's Hasanuddin military commander.
Sari said the plane disappeared shortly after being instructed by air traffic control to correct its approach alignment. “After the last ATC instructions, radio contact was lost and controllers declared the emergency distress phase.” She said rescue teams focused their search around the mountains where the aircraft, with eight crew members and three passengers from the Marine Affairs and Fisheries Ministry aboard, was believed to have deviated from its approach to Sultan Hasanuddin International Airport.
Weather conditions at the time indicated clouds and 8-kilometre visibility, Sari said.
Steep terrain at Bulusaraung National Park linking Maros and Pangkep districts has complicated the search efforts, Nawoko said.Director General of Air Transport, Lukman Laisa, said controllers lost contact with the captain as they attempted to bring the plane back on course.
The official said: “The aircraft was identified not to be on the approach path it should have been, so the air traffic control gave a redirection to the crew to correct the position.
“Air traffic control then conveyed several further instructions. The instructions aimed to bring the plane back to the landing.
“After the submission of the last instructions, communication with the plane was lost.
“Following up on this condition, air traffic control declared an emergency phase in accordance with the applicable provisions and procedures.”
The last signal from the missing plane was received at 11:20am local time, about 12 miles northeast of Yogyakarta airport.
The plane never arrived at its planned destination of Sultan Hasanuddin International Airport, leaving families of those onboard searching for answers.
The missing aircraft was owned by Indonesia Air Transport, which specialises in charter flights for oil and gas businesses.
The plane was on a long-term contract for the government’s Marine and Fisheries Resources Surveillance service before it vanished.
It comes after a Russian military plane crumbled mid-air last month, before crashing into a reservoir.