Investigators have confirmed the new priority search area for missing Malaysia Airlines flight MH370 has moved further south as end-of-flight scenarios indicate it may have spiralled into the southern Indian Ocean.

The Australian Transport Safety Bureau (ATSB) has released a report detailing how the latest analysis of satellite and flight data has narrowed down the search area.

Seven months since the aircraft disappeared on a flight from Kuala Lumpur to Beijing with 239 people on board, the underwater search phase will focus on the southern extremity of a wide area about 1,000 kilometres off Western Australia's northern coast and more than 2,000 kilometres off its southern coast.

One vessel, GO Phoenix, started operations earlier this week, while another, Fugro Discovery, is expected to leave the Fremantle Port at the weekend to head to the most remote part of the search zone.

The third contracted vessel, Fugro Equator, is already carrying out survey work.

Analysis of the data by experts from Australia, Malaysia, the UK and the US continues, with communications and flight data used to determine the first underwater areas to be scoured.

The ATSB report said when all elements of the analysis so far were taken into account, it indicated the aircraft "may be located within relatively close proximity to the arc", although further south than initially thought.

Aviation experts believe the best hope of finding the plane is within the seventh arc, or the final satellite "handshake" from the plane, estimated to be when it was in descent.

"The simulator activities involved fuel exhaustion of the right engine followed by flameout of the left engine with no control inputs," the ATSB said in an update on the flight path analysis.

"This scenario resulted in the aircraft entering a descending, spiralling, low-bank-angle left turn and the aircraft entering the water in a relatively short distance after the last engine flameout."

Ongoing analysis of the satellite data and end-of-flight simulations could result in further changes to where the search was conducted, the ATSB added.

ABC/AFP