Malaysia's defence minister says he is "99.9 per cent" sure the missing Malaysia Airlines flight MH370 will be found in the southern Indian Ocean.

The minister was speaking aboard one of the vessels contracted to carry out the search, GO Phoenix, which is in Fremantle, WA after scanning more than 1,200 square kilometres of the ocean floor.

The minister, Hishamuddin Hussein, said the accuracy of the technology being used in the search gave him confidence the missing plane would be found.

He said as long as the other data was correct, he was close to sure the plane would be found.

"We're looking at satellite technology... the technical committee has got to zoom in into the areas of search, but if the question just now was based on the technology that was available and we are looking in the right place, we're talking about 99.9 per cent," he said.

GO Phoenix was s in port for resupply after spending 10 days conducting underwater search operations in the designated area.

During a brief ceremony on the Phoenix, Hishamuddin Hussein praised the high levels of international co-operation that had taken place.

More than two dozen nations had been involved the search for MH370.

But Mr Hishamuddin said he would like China to play a greater role.

"I would like to see the Chinese flag flying in the search area too, and I think that's not a problem," he said.

"The more assets that we can deploy, the more people that can come on board, partners which traditionally people will say would never work together, we have proven them wrong."

Towfish searches seabed in deep ocean

GO Phoenix's towfish is called a PROSAS surveyor.

The sonar equipment is towed about 100 metres above the seabed, and scans out 1,000 metres to each side, which means a swathe of two kilometres.

Phoenix International president Mike Kutzleb said it also had a multi-beam which looked down, to ensure every square centimetre of the seabed was covered.

"Everything has been going well out there so far, we've had great weather so far, keep my fingers crossed for continued good weather," he said.

"We covered about 1,250 square kilometres when we were out there for the first ten days, when we go out for the typical 20 day mission from now on, we expect to cover approximately twice that much.

"We are having a very high coverage rate with the sonar that we have, but the area is very vast so it's going to take a long time. (We) just put one foot in front of the other."

Mr Kutzleb said he was confident that if any part of the plane were out there, it would be found.

"The quality of the data that we're getting from this sonar is very high," he said.

"That gives us a high degree of confidence that if we go over the aircraft debris field while we're out there, we will be able to detect it."

More than 140,000 square kilometres of what has been described as "the wide search area" has been analysed and mapped.

The Chinese vessel Zhu Kezhen collaborated on this with Fugro Equator, which is still carrying out survey work.

Third vessel to join underwater search

Later this month, the Equator will be mobilised as the third underwater search vessel, joining GO Phoenix and Fugro Discovery.

Australian Transport Safety Bureau's chief commissioner Martin Dolan said analysis of available information was still taking place, so that the best possible search area was being constantly refined.

"We have been working with an international group to analyse the key data on this which is from communications between a ground station and the aircraft," he said.

"We have largely completed that work and also have a good understanding of the likely behaviour of the aircraft at the end of its flight.

"We think we're in the right area, it's not a 100-per cent guarantee, I would agree with the Minister, we've got the technology if we're in the right area to find the aircraft.

"We do want to give closure and certainty [for those] who are grieving the loss of their loved ones in this tragedy, we also want to find out for the future of aviation safety what happened with that aircraft."