of Java, Papua New Guinea and the Solomon Islands.
While the Jindalee Operational Radar Network (JORN) extends part-way across the northern Indian Ocean, government papers online describe it as a "tripwire" in Australia's northern surveillance system, helping underpin the defense of the country from any attack originating from the north.
Local media have said its main use recently has been to track illegal immigrants approaching Australia by boat through the region's largely unguarded northern waters.
The Australian Defence Force was not available for comment on Sunday.
A potential crash site around 1,600 km (1,000 miles) northwest or west of the Australian coast would be well within the search and rescue area of the Australian Maritime Safety Authority (AMSA), one of the largest in the world.
An AMSA spokesman said no request for assistance had been received from Malaysia as of Sunday.