Investigators seeking the wreckage of Malaysia Airlines Flight 370 in the southern Indian Ocean are widening their search area to cover the chance the aircraft fell from the sky at a shallower angle than expected.

It’s possible that “the descent wasn’t in quite such a tight circle as we are assessing,” Martin Dolan, chief commissioner of the Australian Transportation Safety Bureau, said in a phone interview yesterday. That could put the Boeing Co. 777-200 on the sea floor as far as 50 nautical miles (93 kilometers) from the seventh arc, a line drawn over the ocean where satellite communications suggest its fuel ran out.

An extra 40,000 square kilometers (15,500 square miles) have been scanned by ship-based sonars over the past three weeks, adding about 25 percent to a high-priority search zone previously declared complete Oct. 26. That indicates the level of uncertainty still remaining in the hunt for the Malaysian Airline System Bhd. aircraft, which disappeared March 8 with 239 people on board.

“There’s a possibility that it could have gone a bit further” in the few minutes between the engines stalling and the aircraft hitting the sea, Dolan said. “These aircraft travel at hundreds of kilometers an hour, so a few minutes can make quite a difference.”

The nine-month search for the plane, which vanished en route from Kuala Lumpur to Beijing, remains the longest such hunt in modern civil aviation history.

Best Evidence

The best evidence of the plane’s location comes from eight failed connections with an Inmarsat Plc orbiter over the Indian Ocean, showing the plane probably traveled south from the Bay of Bengal before ditching somewhere along an arc to the west of the Australian city of Perth.

The aircraft probably spiraled anti-clockwise into the sea after its right and then its left engines ran out of fuel, the Bureau wrote in an update on the search process Oct. 8.

“Going into an increasingly tight spiral is the most likely behavior,” Dolan said. Even that isn’t guaranteed, Dolan said.

The latest bathymetric scans, using sonars mounted on the search ship Fugro Equator, have widened the Bureau’s high- priority search area to stretch 50 nautical miles rather than 30 nautical miles from the seventh arc. They’ve also extended the zone to the very furthest south the aircraft could have come to rest, Dolan said.

That doesn’t mean investigators expect it to have drifted so far. “All the evidence says the most likely behavior of the aircraft will mean it will be found within 10 nautical miles of the arc,” he said.

Share Trading

The ship-based scan, which has now covered 200,000 square kilometers, is the first part of a two-stage search process. It’s designed to provide an accurate picture of the ocean bottom for side-scan sonar submersibles carrying out the second stage.

Those submersibles, which can cruise as far as four miles below the surface, are towed close to the sea floor to provide higher resolution imagery and have so far mapped about 9,000 square kilometers.

The side-scan search remains the best hope to discover wreckage of the aircraft and the flight data recorders which could explain its disappearance. It will probably be complete once about 40,000 square kilometers has been scanned in April or May, Dolan said.

Malaysia’s sovereign wealth fund Khazanah Nasional Bhd. is restructuring the national airline amid competition from AirAsia Bhd. and falling traffic following the MH370 disaster and the downing of flight MH17 over eastern Ukraine.

The fund has bought out minority investors in the carrier and announced Dec. 5 that outgoing Aer Lingus Plc Chief Executive Officer Christoph Mueller would take over Malaysia Airlines’s top job. Trading in the airline’s shares on the Kuala Lumpur stock exchange will cease after today.

To contact the reporter on this story: David Fickling in Sydney at To contact the editors responsible for this story: Anand Krishnamoorthy at Shamim Adam

Photo Credit: Flight Lieutenant Russell Adams looks out from the cockpit of a Royal Australian Air Force (RAAF) AP-3C Orion aircraft while searching for the missing Malaysia Airlines Flight MH370 over the southern Indian Ocean March 26, 2014. Paul Kane