On March 8 2014, Malaysia Airlines flight MH370 departs Kuala Lumpur International Airport bound for Beijing with 227 passengers and 12 crew on board. Half an hour later, the plane disappears from radar.

A Kiwi oceanographer says MH370 was being "deliberately flown" when the doomed Malaysia Airlines flight ended somewhere over the southern Indian Ocean.

New Zealander Rob McCallum co-founded EYOS Expeditions and works for deep sea and search specialists Williamson & Associates based in Seattle.

McCallum, who was involved in a successful search for Air France Flight 447 wreckage in 2011, is also calling for the Australian Transport Safety Board (ATSB) to release the MH370 data set of search operations for analysis by third parties.

REUTERS A Malaysia Airlines Boeing 777, the same model as the missing aircraft. A piece of debris found along the eastern African coast between Mozambique and Madagascar may be from the tail section of MH370.

The New Zealander has previously criticised the taxpayer-funded search, which aims to cover 120,000 square kilometres, but denies sour grapes and said the failure to release data was unprecedented in a commercial aviation mystery.

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STUFF The area in the Southern Ocean where the extensive search MH370 took place.

Williamson & Associates, also known for finding HMAS Sydney, was one of the unsuccessful bidders for the search contract, worth about $55m. The search is expected to cost about $195m.

MH370 search vessels are retracing some areas that have already been swept by sonar, in a search the bureau and the Joint Agency Coordination Centre have described as an immense task.

Speaking from Indonesia, McCallum said he believed the searchers may be doubling back to look at a "debris field" target previously deemed as geological.

FUGRO A short film from contractor Fugro on the technology used for deep towing searches.

McCallum's MH370 theory?

"I think there has been human intervention and it's been deliberately flown and would have disappeared [completely] without the [forensic satellite analysis]."

"The important point is that this area has been searched before.

EYOS Rob McCallum has called on the Australian authorities to release raw data.

"When you say that area's searched again it means they are really searching, searching again for something they missed.

"In our industry people always ask us can you find this target? What we will do is give you a 100 per cent guarantee that where we've searched it's not there.

"The primary role is to be rigorous in your approach so you can write it off.

ATSB The ''seventh arc'' and a highlighted expanded area, the focus of the search operation for flight MH370.

"That's not happened in this case."

"They have used a little tiny pen light because they are interested in resolution. We would use a very broad search tool, find the target and then go in with a higher resolution tool."

THE SEARCH SO FAR

GEOSCIENCE AUSTRALIA A short film describing the processes of bathymetric mapping and side scan sonar, used to gather data within the search area for MH370.

The search for the Boeing 777 aircraft, which disappeared in March 2014 with 239 people on board, is led by the ATSB, who appointed Dutch company Fugro to conduct the search.

Fugro has three deep-sea search ships in the region and another vessel, Dong Hai Jiu 101, has been deployed by China. Ships have so far collected about 20 million gigabytes (20 petabytes) of data.

"Since then $100 million has been spent on a data set nobody has ever seen," McCallum said.

Australian Transport Safety Bureau/CSIRO Drift analysis of ocean currents concluded debris may be found as far west of the search area as La Réunion Island.

He said deep sea search techniques use a variety of sonar types, like searching a dark room with a pen torch, for higher definition, or a wide-beam torch for less definition and a larger field of vision.

The ATSB and the contractor have vigorously defended their technique and sonar technology, which was supplied by the same firm used to find the wreckage of Air France Flight 447 in the Atlantic.

Satellite data from Inmarsat was used to decide the search area by analysing a series of "handshakes" between the aircraft and orbiting hardware to lead the ATSB to identify the most likely flight track and the search area.

The seventh and final handshake was used to extrapolate the most likely flight path and the basis for marking a search area.

Data used, for example, to search for military material or valuable shipwrecks was understandably commercially sensitive but the MH370 data was government funded, McCallum said.

The handful of experts around the world capable of understanding and interpreting raw sonar search material would be happy to test the data, he said.

"There's an incredible amount of goodwill in all quarters to see this thing finished.

"It's the world's biggest aviation mystery."

Previous reports of criticism of the ATSB, the capabilities of the contractor and the approach to the search have been "corrected" by the bureau, which denied Fugro was the wrong choice.

Fugro has also stated its technology is appropriate and its methods are rigorous.

Williamson & Associates' founder Mike Williamson said the firm cautioned the ATSB during the initial stages of the tender process.

"We cautioned the ATSB the worst possible outcome is they search an area and the overlap was insufficient to know they had 100 per cent coverage and they come up with no target. They could not say it wasn't there.

"We warned them two years ago. We were dismissed as sour grapes.

"Probability of detection is the paramount factor. That's the most important thing you're playing for."

The search area lies in an inhospitable region of the ocean, the Roaring Forties, and the sea floor can be as deep as 6km below the surface amid underwater volcanoes, cliffs and ridges.

The ATSB and the JACC did not respond to questions.

Malaysia, ultimately, has responsibility for establishing the how and why.

Air France Flight 447 disappeared in June 2009 with 228 people on board. It was not until two years later that search teams managed to recover the black boxes, used to piece together the fate of those bound for Paris from Rio de Janeiro and the sequence of errors that led the Airbus to stall mid-flight.