The sonar search for the missing Malaysia Airlines flight is about to resume, with a Malaysian ship the first to begin scouring the Indian Ocean for MH370.

The vessel, GO Phoenix, is expected to arrive at the newly defined search area far off the Western Australia coast on Wednesday.

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After analysis of satellite data from the plane was refined, it was concluded the aircraft may have entered the water in an area south of what was initially considered the top priority search zone.

GO Phoenix is scheduled to stay there for about 20 days before sailing to Fremantle to be resupplied.

It will be joined by the Fugro Discovery, which is on its way to WA after undergoing fit-out work in South Africa.

The Fugro Discovery is expected to arrive in Fremantle on Thursday.

The Fugro Equator will join the search around the end of October once it finishes sea floor mapping work currently under way.

MH370 disappeared with 239 people on board during its March 8 flight from Kuala Lumpur to Beijing.