What could have happened to flight MH370?

We all know the story of MH370: A loaded Boeing 777 – with 239 people on board - departs at midnight from Kuala Lampur, en route to Beijing. About an hour into the flight, across the gulf toward Vietnam, the plane goes dark, meaning the transponder and secondary radar tracking go off. Two days later, reports emerge that Malaysian military radar has tracked the plane on a southwesterly course back across the Malay Peninsula into the Strait of Malacca.

And yet, 11 days since that fateful night, speculation about what could have happened to flight MH370 is still rife. Theories of engine failure, hijacking and even terrorism have all been raised. More worrying still is the fact that none of these theories are yet conclusive.

Here, former pilots and aviation experts look at some of those theories.

1. It landed in the Andaman Islands

The plane was apparently at one stage heading in the direction of India's Andaman and Nicobar Islands, the most easterly part of Indian territory, which lies between Indonesia and the coast of Thailand and Burma. With over 570 islands – only 36 of which are inhabited – the areas is an isolated spot. It has been reported that military radar there might not even have been operating, as the threat level is generally perceived to be low.

Steve Buzdygan, a former BA 777 pilot suggests that it would be the ideal spot for the pilots to land the plane secretly in the case of a hijacking. “It would be difficult, but not impossible, to land on the beach,” he says.

The editor of the islands' Andaman Chronicle newspaper dismisses this notion claiming that the plane would have been spotted. He also believes that monitoring by the Indian military would prevent an airliner being able to land there unnoticed.

2 It flew to Kazakhstan

Light aircraft pilot Sylvia Wrigley, author of ‘Why Planes Crash’, says landing in a desert might be possible and certainly more likely than landing on a beach somewhere. The failure so far to release a cargo manifest has created wild rumours about a valuable load that could be a motive for hijacking. There has also been speculation that some of those on board were billionaires.

The Kazakh Civil Aviation Committee, however, issued a statement dispelling this theory claiming the plane would have been detected. Furthermore, in order for the plane to have reached Kazakhstan, it would have needed to pass over the airspace of India, Pakistan and Afghanistan.

But Wrigley points out that there may be weak links in the radar systems of such countries. “A lot of air traffic control gear is old. They might be used to getting false positives from flocks of birds and, therefore, it would be easy to discount it,” she says.

3. It flew southward

The final satellite “ping” suggests the plane was still operational for at least five or six hours after leaving Malaysian radar range. For Norman Shanks, former head of group security at airports group BAA, and professor of aviation security at Coventry University, the search should therefore start from the extremes of the corridors and work up, rather than the other way around. He thinks the southern corridor is more likely for a plane that has so far avoided detection by radar.

4. It landed in the Taklamakan Desert

There has been speculation on forums that the plane could have been commandeered by China's Uighur Muslim separatists. Out of the plane's 239 passengers, 153 were Chinese citizens. One possible destination in this theory would be China's Taklamakan Desert. The region has no shortage of space far from prying eyes. But again, this theory rests on an extraordinary run through the radar systems of several countries.

5. It flew towards Langkawi Island because of a fire or other malfunction

The loss of transponders and communications could be explained by a fire, aviation blogger Chris Goodfellow has suggested. The left turn that the plane made, deviating from the route to Beijing, could have been a bid to reach safety, he argues. “This pilot did all the right things. He was confronted by some major event onboard that made him make that immediate turn back to the closest safe airport.”

In this theory it would be assumed that the airliner did not make it to Langkawi and crashed into the sea but this has also been disputed. If the course was changed during a major emergency, one might expect it to be done using manual control. But the left turn was the result of someone in the cockpit typing “seven or eight keystrokes into a computer on a knee-high pedestal between the captain and the first officer, according to officials", the New York Times reported. The paper says this “has reinforced the belief of investigators - first voiced by Malaysian officials - that the plane was deliberately diverted and that foul play was involved.”

6. The plane is in Pakistan

Like the Kazakhstan theory, this theory seems far-fetched, not least because the junction between Indian and Pakistani air space is one of the most watched sectors in the world by military radar. And despite the remoteness and lawlessness of northern Pakistan, the region is watched closely by satellites and drones. It seems scarcely believable to think an airliner could get there unspotted.

Pakistan has strenuously denied that this would even be possible. The country's assistant to the prime minister on aviation, Shujaat Azeem, has been reported as saying: “Pakistan's civil aviation radars never spotted this jet, so how it could be hidden somewhere in Pakistan?”

7. The plane hid in the shadow of another airliner

Aviation blogger Keith Ledgerwood believes the missing plane hid in the radar shadow of Singapore Airlines flight 68. The Singaporean airliner was in the same vicinity as the Malaysian plane, he argues. “It became apparent as I inspected SIA68's flight path history that MH370 had maneuvered itself directly behind SIA68 at approximately 18:00UTC and over the next 15 minutes had been following SIA68.” He believes that the Singaporean airliner would have disguised the missing plane from radar controllers on the ground.

The Singapore Airlines plane flew on to Spain. The Malaysian jet could have branched off. “There are several locations along the flight path of SIA68 where it could have easily broken contact and flown and landed in Xinjiang, Kyrgyzstan, or Turkmenistan,” Ledgerwood argues.

However, Professor Hugh Griffiths, radar expert at University College London, says that there is a difference between military and civilian radar. Civilian radar works by means of a transponder carried by the aircraft - a system known as secondary radar.

It is possible military radar would be able to pick up that there were two objects, he says. “It might be able to tell the difference, to know that there are two targets.” If this happens, though, there is then the question of how this is interpreted on the ground. Is it a strange echo that would be discounted? When the Japanese attacked Pearl Harbor in 1941, although the US radar operator detected the incoming aircraft, they were dismissed as US bombers arriving from the mainland.

8. There was a struggle

One of the hardest things to account for so far with an innocent explanation is the way the plane was flown erratically. It went far above its “ceiling”, flying at 45,000ft (13,716m) before later flying very low. Big fluctuations in altitude suggest there might have been a struggle, says Buzdygan. Post-9/11, cockpit doors have been strengthened against the possibility of hijack but there are still scenarios where access could be gained. Pilots talk to each other “over a beer” about how they'd deal with hijackers, he says. Buzdygan would have had no qualms about flying aggressively to try to resist a hijack. “I'd try to disorientate and confuse the hijackers by throwing them around,” he says.

 9. The passengers were deliberately killed by decompression

Another theory circulating is that the plane was taken up to 45,000ft to kill the passengers quickly, former RAF navigator Sean Maffett says. The supposed motive for this might have been primarily to stop the passengers using mobile phones, once the plane descended to a much lower altitude. At 45,000ft, the Boeing 777 is way above its normal operating height. And it is possible to depressurise the cabin, notes Maffett. Oxygen masks would automatically deploy. They would run out after 12-15 minutes. The passengers - as with carbon monoxide poisoning - would slip into unconsciousness and die, he argues. But whoever was in control of the plane would also perish in this scenario, unless they had access to some other form of oxygen supply.

10. The plane will take off again to be used in a terrorist attack

One of the more outlandish theories is that the plane has been stolen by terrorists to commit a 9/11 style atrocity. It has been landed safely, hidden or camouflaged, will be re-fuelled and fitted with a new transponder before taking off to attack a city. It would be very hard to land a plane, hide it and then take off again, Maffett suggested. But it can't be ruled out. “We are now at stage where very, very difficult things have to be considered as all sensible options seem to have dropped off,” he says. It is not clear even whether a plane could be refitted with a new transponder and given a totally new identity in this way, he says. Others would say that while it is just about feasible the plane could be landed in secret, it is unlikely it would be in a fit state to take off again.