He told Channel 5’s ‘Flight MH370’: “I think it’s highly likely a hijack took place – and again, there’s four options for the hijack.
“One is a hijack of the aircraft through a crew member.
“The second is a hijack coming from a passenger.
“A third option, which is a fairly unusual one, would be a stowaway.
“And then of course the fourth option is an electric takeover of the aircraft from a ground-based station.”
That last option is intriguing as it would mean investigations into those on board could prove fruitless.
A recent report by The Atlantic suggested the plane’s captain Zaharie Ahmad Shah could have been responsible.
It claimed Mr Shah had carried out a similar flight on his home flight simulator and that he had been struggling with mental health difficulties.
If Mr Shah was responsible for MH370’s disappearance, this would tie into the first hijack option.
Investigations into flight MH370 have also looked at passengers, including two who were discovered to have been using fake passports.
However, one of them was found to have been trying to emigrate to Europe and not considered likely to be part of a terrorist organisation.
Aviation expert Jeff Wise, suggested that MH370’s disappearance was a ploy by the Russian government to distract from the conflict in Crimea.
He said: “There could have been a Russian on board who interfered with the systems and left a false trail of breadcrumbs.”
There was one known Russian passenger, Nikolai Brodskii.
However, the plane could also have been hijacked electronically.
Risk management consultant Dr Sally Leivesley told the documentary that without the correct documentation, we do not know who had access to the plane directly before take-off.
She suggested it might have been possible for a saboteur to sneak on with a USB stick and launch a cyberattack on the plane.
She said: “We know from the Malaysian government reports there was a maintenance activity in it February, but in the immediate period before the plane took off we don’t have that history.
“We need to know who had access to the plane.
“Was there an opportunity for someone to get on with a USB stick or in other ways to initiate a cyberattack on the plane so it would never reach its destination?”