PERTH, Australia (AFP) ― The search for a Malaysian airliner intensified Sunday, 22 days after it vanished with 239 people on board, as relatives of Chinese passengers arrived in Malaysia to demand answers about their fate.

Eight ships ― the largest number so far ― and 10 planes from six countries were sweeping a vast expanse of the Indian Ocean off Australia for wreckage from the Malaysia Airlines Boeing 777.

Hopes of finding physical evidence of a crash have been repeatedly raised by debris sightings, then crushed as the items turned out to be random sea junk such as fishing gear.

As the hunt resumed 1,850 kilometers west of Perth, Australia said its former military chief Angus Houston would head a new unit to help in the search, which involves the militaries of seven nations ― Australia, China, Malaysia, Japan, New Zealand, South Korea and the United States.

Prime Minister Tony Abbott said Houston would lead the new Joint Agency Coordination Center based in Perth.

Houston will coordinate the often delicate diplomatic contacts between search participants, and ensure families get all the information and help they need.

About two-thirds of those on board were Chinese and their loved ones have complained bitterly about what they see as Malaysia’s secretive and incompetent handling of the search. 

Thirty-nine relatives arrived Sunday in Malaysia to push for more answers. They are particularly angry at the announcement on March 24 by Malaysian Prime Minister Najib Razak that ― based on detailed British analysis of satellite and other data ― the plane had been lost at sea.

Clinging to shreds of hope, several desperate relatives refuse to accept this until wreckage from the jet is found.

“Can you tell us precisely in which countries the aircraft could have landed?” screamed a man at a Malaysian briefing for relatives Saturday in Beijing.

Abbott said the Australian government “won’t rest until we’ve done everything we reasonably can to get those families and to get the wider community of the world a little more peace and a little more insight into exactly what happened.”

International protocols mean Malaysia is officially in charge of the search, but Abbott made clear that Houston was available “to oversee the overall search and investigation effort” if asked.

Authorities continued to pour resources into the operation, which is scouring an area about the size of Norway. An Australian ship with U.S.-supplied equipment on board to locate the “black box” flight recorder was due to depart from Perth later Sunday.

Two Malaysian C-130 Hercules aircraft were to join the operation for the first time.

“Until items are picked up by a ship and assessed by expert investigators, no conclusions as to their origin can be made,” said New Zealand’s Air Vice Marshal Kevin Short.

“It’s difficult and demanding work, scanning the ocean for small items, even flying low over the water at comparatively slow speeds. It requires total concentration.”

The search had moved Friday to a new sea zone after fresh data indicated the plane was flying faster than first thought before it is presumed to have run out of fuel and plunged into the sea.

But debris sightings by Chinese, Australian and New Zealand planes on Saturday did not yield any solid clues, compounding the frustration of families.

Flight MH370 disappeared on March 8 during a flight from Kuala Lumpur to Beijing, in one of aviation’s greatest mysteries.

Malaysia believes it was deliberately redirected by someone on board before being flown thousands of kilometers southward, but nothing else is known.

A sighting of wreckage could bring closure for relatives. It could also help searchers find the main body of the plane and the flight recorder before its battery-powered “pinger” locator stops working.

The battery normally lasts one month. But in a rare piece of good news, Captain Mark Matthews --- the U.S. Navy supervisor of salvage and diving -- said that while the pinger is certified for 30 days, it could last up to 15 days longer than that.

Fifty Malaysians were also on the plane and signs of mourning are everywhere in the country’s capital.

Teams and spectators at the Malaysian Grand Prix Sunday afternoon were to observe a minute’s silence for the victims.

Drivers wore helmet stickers reading “Pray for MH370.”