A top airline boss has voiced doubts about the search for doomed airliner MH370 and said the plane may not even be in the southern Indian Ocean.

Sir Tim Clark, head of Emirates Airline, told Germany's Spiegel Online it was possible someone in the hold, or any passenger, took control of the plane.

He said the plane should never have been allowed to enter a "non-trackable" situation.

And the Emirates boss said there was no evidence the plane even headed for the southern Indian Ocean, as is commonly believed.

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Sir Tim said it was bizarre nothing had been found despite extensive searches in the southern Indian Ocean. The flight, carrying 239 passengers and crew, disappeared on March 8. New Zealanders Ximin Wang and Paul Weeks were among those on board.

Sir Tim told Spiegel Online there had not been an overwater incident in the history of civil aviation - apart from the disappearance of Amelia Earhart in 1939 - that was not at least 5 or 10 per cent trackable.

But MH370 has simply disappeared. "That raises a degree of suspicion. I'm totally dissatisfied with what has been coming out of all of this.

"We have not seen a single thing that suggests categorically that this aircraft is where they say it is, apart from this so-called electronic satellite 'handshake', which I question as well," Sir Tim said.

Spiegel Online asked why pilots would spend five hours heading straight for Antarctica if MH370 was under control.

"I am saying that all the 'facts' of this particular incident must be challenged and examined with full transparency," he responded.

He ruled out any suggestion the Boeing 777 needed its communication platforms overhauled. Sir Tim said an additional tracking system was not needed and "MH370 should never have been allowed to enter a non-trackable situation".

"The transponders are under the control of the flight deck," he said. "These are tracking devices, aircraft identifiers that work in the secondary radar regime. If you turn off that transponder in a secondary radar regime, that particular airplane disappears from the radar screen. "

The outspoken airline chief promised more candid commentary on the issue.

"I will continue to ask questions and make a nuisance of myself, even as others would like to bury it," he said. "We have an obligation to the passengers and crew of MH370 and their families."

Four months after MH370 disappeared, 298 passengers died when flight MH17 was shot down over Ukraine.

Sir Tim said Malaysia Airlines would find it difficult to recover.

"We as an industry need to find a way to help these guys sort out their problems. But with that kind of brand damage, it's extraordinarily difficult."