Malaysian Prime Minister Najib Razak is heading to Australia for briefings on the search for the missing plane.

Malaysian Prime Minister Najib Razak is set to arrive in Perth before he visits the RAAF Pearce air base, the departure point for the seven-nation air search for the Malaysia Airlines plane.

Mr Najib will arrive on Wednesday afternoon and will stay until Thursday.

He will receive a briefing from joint agency co-ordination centre head, retired Air Chief Marshal Angus Houston.

“The co-operation with Malaysia has been first class,” Air Chief Marshal Houston told ABC Radio on Wednesday.

He said that until surface debris was found, authorities were unable to narrow the search area and start to exploit underwater technology.

“The reality is it’s the most complex and challenging search and recovery operation I’ve ever seen,” he said.

“If we don’t find anything on the surface, we’ll have to think about what we do next.”

Meanwhile, a fourth Australian ship, Seahorse Standard, has departed for the search zone to join a flotilla of three other Australian vessels and more than six Chinese ships.

Malaysian frigate KD Lekiu is also en route.

Australian defence vessel Ocean Shield is expected to reach the search zone on Friday with a pinger locator to find flight MH370’s black box.