A fire probably broke out onboard the missing Malaysia Airlines Flight 370 and the pilot was trying to save the plane by making a left turn to land at the Malaysian island of Langkawi, said a fresh theory which has made its rounds online.

But the flight crew might have been overcome by smoke and the aircraft continued flying on autopilot until it ran out of fuel, or the fire could have destroyed the control surfaces and it crashed, claimed Mr Chris Goodfellow, who has 20 years experience as a Canadian Class-1 instrumented-rated pilot for multi-engine planes.

In his article which first appeared on Google+ and was reproduced in the online edition of Wired magazine, he wrote: "For me, the loss of transponders and communications makes perfect sense in a fire. And there most likely was an electrical fire.

"In the case of a fire, the first response is to pull the main busses and restore circuits one by one until you have isolated the bad one. If they pulled the busses, the plane would go silent. It probably was a serious event and the flight crew was occupied with controlling the plane and trying to fight the fire."

Another possible cause of fire was an overheat on one of the front landing gear tires which blew on takeoff and started burning slowly, he said.

"When I saw that left turn with a direct heading, I instinctively knew he was heading for an airport. He was taking a direct route to Pulau Langkawi, a 13,000-foot airstrip with an approach over water and no obstacles," he added.

He cited a previous accident in Nigeria which involved a DC8 that had a landing gear fire on takeoff. A tire fire, he said, would produce horrific, incapacitating smoke. "Yes, pilots have access to oxygen masks, but this is a no-no with fire. Most have access to a smoke hood with a filter, but this will last only a few minutes depending on the smoke level."

He went on to say: "What I think happened is the flight crew was overcome by smoke and the plane continued on the heading, probably on George (autopilot), until it ran out of fuel or the fire destroyed the control surfaces and it crashed. You will find it along that route - looking elsewhere is pointless."

Malaysian police investigations have failed to turn up any red flags on 53-year-old Zaharie Ahmad Shah, the captain of the missing Malaysia Airlines plane, or co-pilot Fariq Abdul Hamid, 27. Investigators are now focusing on the possibility of foul play. -- PHOTOS: THE STAR/JONTI ROOS

Reports said investigators are scrutinising radar tapes from when the plane first departed Kuala Lumpur because they believe the tapes will show that after the plane first changed its course, it passed through several pre-established "waypoints", which are like virtual mile markers in the sky.

Some experts said that would suggest the plane was under control of a knowledgeable pilot because passing through those points without using the computer would have been unlikely.

While Mr Goodfellow's theory has its fair share of support, some believe that the argument is flawed.

Mr Jeff Wise, writing for Slate magazine, pointed out that the plane was said to have made a series of turns after the first left turn. "Such vigorous navigating would have been impossible for unconscious men," he said,

"Goodfellow's theory fails further when one remembers the electronic ping detected by the Inmarsat satellite at 8.11 on the morning of March 8," he added, pointing to analysis of the pings provided by the Malaysian and United States governments which narrowed the location of MH370 at that moment to one of two arcs, one in Central Asia and the other in the southern Indian Ocean.

"As MH370 flew from its original course towards Langkawi, it was headed towards neither," he said. "Without human intervention - which would go against Goodfellow's theory - it simply could not have reached the position we know it attained at 8.11am."

Meanwhile, some media agencies - including The New York Times, Bloomberg News and ABC News - quoted US officials as saying that the plane's sharp turn to the west was achieved using a computer system on the plane, rather than manually operating the plane's controls.

Whoever altered flight 370's path had typed seven or eight keystrokes into a computer situated between the captain and the co-pilot, said The New York Times, quoting the officials. That has reinforced the belief of investigators that the plane was deliberately diverted and that foul play was involved.

When the chief executive officer of Malaysia Airlines, Mr Ahmad Jauhari Yahya, was asked on Tuesday about the possibility that the turn off course was programed by someone in the cockpit, he did not give a definitive answer. "As far as we're concerned, the aircraft was programed to fly to Beijing," he said. "Once you're in the aircraft, anything is possible."