A Singapore aircraft en route from Sibu, Sarawak, to Seletar Airport with a pilot instructor and two trainees on board was intercepted by Indonesian fighter jets yesterday.
The C90GTi King Air plane owned by Singapore Technologies (ST) Aerospace and operated by its pilot training arm, Pacific Flight Services, was subsequently instructed to land in Pontianak, West Kalimantan.
The Indonesian authorities say that the plane was flying over the country's airspace without the necessary flight permits.
As of 10pm last night, the aircraft had yet to be released.
Confirming the incident, a spokesman for ST Aerospace told The Straits Times that the required approvals had been duly sought before the flight.
"We would like to clarify that we filed the flight plan in accordance with airspace regulations through the Civil Aviation Authority of Singapore and have been operating this route for a number of years without prior notification from the authorities of any issue for using this route," she said.
The incident happened during a return route familiarisation training flight, as the instructor and pilot trainees were passing through a portion of Indonesian airspace, which is in the filed flight plan, she said.
According to industry experts, the norm is that the aircraft operators will file their flight plans through the civil aviation regulator of the country from which they depart.
The information is then conveyed to the authorities overseeing the skies along the path.
The Straits Times understands that the Singapore aircraft was flying at an altitude of 6,100m to 7,600m when it was intercepted by the Indonesian Air Force's two Sukhoi 27/30 Flanker TNI AU jets.
In an incident report posted on its website, the Indonesian Air Force said that although the plane was overflying airspace managed by Singapore air traffic controllers, it was inside Indonesia's sovereign skies.
This meant that the flight needed approval from the Indonesian authorities, which was allegedly not obtained.
ST Aerospace is assisting the authorities in the investigation and will provide more information when the investigation is completed, the company's spokesman said.
This is the second time in a week that the Indonesian Air Force has intercepted a foreign aircraft for allegedly flying without the necessary permits.
Last Wednesday, an Australian private jet flying from Darwin to Cebu in the Philippines was forced to land in Manado, North Sulawesi, after two Sukhoi fighter jets were scrambled from Makassar airbase to intercept it.
The owner of the Beechcraft 95, who was on board, and the pilot were questioned by military investigators and subsequently handed over to the airport authorities for further interrogation.
They were later released but it remains unclear whether they will face any charges.