By David Learmount
Flightglobal
17 April, 2014

The least unlikely cause for the disappearance of MH370, based on what little we know about the final flight, is that a person with a sharp mind and a plan, but who was emotionally unbalanced, took control of the aeroplane.

It could have been one of the pilots, or someone else on board who had the means to persuade the pilots to depart from official cockpit security procedures, possibly in a friendly way.

Cabin crew? Nobody knows, and there is certainly no direct evidence.

There is some circumstantial evidence for the Malaysian authorities’ belief that MH370′s disappearance was the result of ”deliberate action by someone on board”. The most publicised bits of circumstantial evidence are the switching off of the ACARS and then the transponder, followed immediately by a marked departure from the aircraft’s planned route. And this combined with radio silence.

The “emotionally unbalanced person” theory is based on the fact that no-one can imagine the motivation for masterminding what has happened, because no obvious purpose appears to have been served by it. But somebody who is suicidal or otherwise in a disturbed state does not follow normal logic.

The other argument for this theory is historical. There have been many cases in which pilots of aeroplanes carrying passengers have committed suicide by deliberately crashing the aircraft: a Silk Air 737 pilot, an Egyptair 767 pilot, a Royal Air Maroc ATR42 pilot, and last year a LAM Mozambique Embraer 190 pilot.

There is also a history of persons – other than the pilots – with a grudge bringing aeroplanes down: a Pacific Southwest Airlines BAe 146 in 1987, and Ethiopian Airways 757 in 1996. Then there was 9/11 where the perpetrators had a grudge against an entire country.

There is no record – yet – of someone bringing down an ordinary airline flight for the purpose of killing a specific person or group on board.

Staying with the deliberate action theory, if the person responsible had a reason to want no-one ever to find out what really happened, the flight path followed by MH370 would be a brilliant plan.

Commentators have advanced many theories as to how the perpetrator kept everyone on board quiet while carrying out his plan, including incapacitating them by deliberately depressurising the aircraft at high altitude. These theories are guesses, but this particular one has the attraction of not being able to be ruled out.

But there is another way that could have been effective for some hours if the means of taking control was quietly achieved. At 02:00h the passengers would have been sleeping or trying to sleep, not worrying about which way the aeroplane was heading, and most would stay that way until dawn or beyond.

But will we find MH370?

Look at the facts: no floating wreckage has been found nearly six weeks later.

The accuracy of the satellite information on which the search area has been calculated is far from guaranteed, so we may not be looking in the right place, and all the civil and military parties to the search know this.

It is hard enough finding wreckage in the deep ocean when you know where the aircraft was when it went missing, like AF447. In that case floating wreckage was discovered within a couple of days, but it took two years to find the wreck on the sea floor even when the last known position of the aircraft was a fact in which the search teams could have confidence.

AF447 belly-flopped into the water at at a vertical speed of about 120kt (220km/h), with very low forward speed, so the wreckage parts were quite large and thus easy to detect on the surface and on the sea bed. Fortunately for the searchers the main sea-bed wreckage came to rest on a firm, flat plain among sub-sea mountains.

We have no idea how MH370 impacted the water, but if it hit the surface much faster than AF447 and with a nose-down attitude, the pieces would be smaller and thus more difficult to detect.

To add to the searchers’ difficulties, oceanographers report that this area of the sea bed is very silty, and aircraft parts, especially heavy ones like the engines, could sink into the silt making detection by sonar even more difficult.

If we ever find parts from MH370, it may be when seat-cushions or other lightweight debris washes up on the shore of Australia or Antarctica. Unfortunately I think this is the most probable scenario.

Can we do something to prevent this in future? It is not as straightforward as people think.