MELBOURNE, Australia — Indonesia, Malaysia and the Philippines have officially marked the launch of trilateral air patrols over the troubled waters of the Sulu Sea, with a ceremony held at Malaysia’s Subang Air Base and attended by the defense ministers of all three countries.

Known as the Trilateral Air Patrol, or TAP, it follows the launch of maritime patrols by the three nations that began in June. It is an additional aspect of the Trilateral Cooperative Arrangement between the Southeast Asian nations.

According to a news release issued by the office of Malaysia’s defense minister, Hishammuddin Hussein, the TAP comprises of two aspects: namely joint air patrols conducted with the presence of aircrew from the participating national on board an aircraft, as well as coordinated air patrols by the respective air forces within their respective borders.

The former is a monthly flight with each participating country taking turns contributing aircraft. Malaysia will kick off the joint patrols with a flight in November, followed by the Philippines in December and Indonesia in January 2018.

The trilateral maritime and air patrols were initiated in response to fears that the Islamic State group will use the Sulu Sea to move fighters between the three countries, which all have coastlines along the Sulu Sea. ISIS-linked militants had seized the southern Philippine city of Marawi in late May, triggering a counteroffensive from the army to take back the city, which continues to this day.

The area has in recent times also seen increased piracy, smuggling and transnational banditry; the Malaysian defense minster has previously said the TAP and maritime patrols will continue as long as they are needed.

However, Collin Koh, a research fellow at Singapore’s S. Rajaratnam School of International Studies’ Maritime Security Programme, told Defense News that should the patrols be needed for an extended period of time, all three participants will likely “face capacity shortfalls, given the vast maritime zones and diverse areas of maritime interest they are responsible for.”

Malaysia operates a pair of Beechcraft B200T Super King Airs fitted for maritime patrol, while Indonesia’s Air Force and Navy combined have eight CASA/IPTN CN-235s and a small number NC-212s maritime patrol and surveillance aircraft.

With the Philippines having no specialized maritime aircraft of its own, Koh noted that the three countries will likely need to use transport aircraft like the Lockheed Martin C-130 Hercules airlifter to plug the gap in specialized maritime surveillance aircraft in their respective inventories to carry out the air patrols — although the transports lack the “specialized maritime surveillance equipment such as surface search radars or electro-optical sensors that allow all-weather, day-and-night surveillance, especially when targeted at such small surface targets as a speedboat typically used by militants and other lawless elements in the region.”

Both Hussein and Indonesian Defence Minister Ryamizard Ryacudu have said neighboring Singapore and Brunei have been asked to take part in the maritime patrols, although both countries have not committed, with the former having instead offered as support for patrols the use of its sophisticated Information Fusion Centre, which collects and analyses information on vessels at sea around the world.