As the families of the 239 victims onboard the missing Malaysia Airlines jet mark eight years since they lost their relatives, the search for answers continues.

The respected aviation security expert, Philip Baum, has given The Independent the five possible scenarios that he believes are most likely. Here, each is evaluated.

Pilot-assisted suicide

Many people have focused on the aircraft’s commander, Captain Zaharie Shah. He was 53 years old when he took the controls of MH370 and departed from Kuala Lumpur, destination Beijing. In his care were 227 passengers and 11 other crew members.

A common theory is that Captain Shah locked the first officer out of the flight deck. He switched off the communications systems that were designed to keep MH370 in touch with air-traffic controllers; donned an oxygen mask; and depressurised the aircraft. At an altitude higher than Everest, the passengers and other crew would soon perish from from oxygen deficiency (hypoxia).

The captain then, the theory goes, flew the aircraft along the frontier between Thailand and Malaysia to avoid raising the interest of the military on either side, before turning south to a location where he believed it would never be found.

But the official report says: “There was no known history of apathy, anxiety, or irritability. There were no significant changes in his lifestyle, interpersonal conflict or family stresses.”

The first officer was 27-year-old Fariq Abdul Hamid. He was on his first Boeing 777 mission without a training captain overseeing him, and had flown the aircraft only five times before. The investigators said his “ability and professional approach to work was reported to be good”. It seems unlikely that someone with such limited experience of the aircraft would be able to pull off such a plan.

While sadly there have been a number of crashes perpetrated by suicidal pilots – most recently the tragic destruction of Germanwings flight 9525 from Barcelona to Dusseldorf, in which the first officer killed himself and 150 others – never has the subsequent crash been so delayed from the moment of seizure.

Hijacking by the pilot with the intention of landing, surviving and escaping

While it is difficult to find any precedent for this theory, it is feasible that one of the pilots intended to land or ditch the aircraft in a survivable state but bungled it and was incapacitated by hypoxia along with the others onboard. Yet it is difficult to conceive of a possible motive for such an audacious mission.

Besides, the investigators concluded: “There is no evidence to suggest that the PIC [pilot in command, ie captain] and FO [first officer] experienced recent changes or difficulties in personal relationships or that there were any conflicts or problems between them.

“There had been no financial stress or impending insolvency, recent or additional insurance coverage purchased or recent behavioural changes for the crew.”

The investigators also analysed both pilots’ radio conversations and say they detected “no evidence of anxiety or stress”.

In addition, the final report notes: “It is not possible to deactivate automatic deployment of the masks from the cockpit.” The oxygen masks are set automatically to drop in the event of a severe fall in cabin pressure, which would have given the passengers and crew some time to try to communicate with the ground.

Hijacked by a passenger or member of cabin crew

Given the large number of passengers onboard, as well as 10 cabin crew, there is a wide range of possible motives. Standard aviation security measures were in place at Kuala Lumpur International Airport. As the tragic events of 9/11 showed, the fact of having passed through a checkpoint does not mean that the passenger poses no threat to the aircraft and the people onboard.

There were a total of 227 passengers (including three children and two infants) on board, with the majority of them from China, followed by Malaysia.

Two Iranian passengers were travelling on passports stolen from an Italian and an Austrian respectively, but they appear to have been illegal migrants who were keen to reach the West rather than harbouring any malicious intent.

All 10 members of cabin crew were married with children, which some have said implies they were unlikely to have hijacked the aircraft.

Hijacked remotely in a sophisticated act of cyberterrorism

This is where feasible theories and unfeasible conspiracy theories begin to converge.

In 2003, Boeing took out a “Patent on Remote Control Take-over of Aircraft”, designed to foil hijack attempts. “The ‘uninterruptible’ autopilot envisioned by the patent could be activated, either by pilots, onboard sensors or remotely via radio or satellite links by the airline or government agencies if there were attempts to forcibly gain control of the cockpit.

“This system once activated would disallow pilot inputs and prevent anyone onboard from interrupting the automatic takeover. Thus, the personnel onboard could not be forced into carrying out the demands of any unauthorised person(s).”

The converse is that criminals on the ground might be enabled by such technology to take over the aircraft.

But the aircraft maker told investigators: “Boeing has confirmed that it has not implemented the patented system or any other technology to remotely pilot a commercial aircraft and is not aware of any Boeing commercial aircraft that has incorporated such technology.”

The report concludes: “There is no evidence to support the belief that control of the aircraft 9M-MRO (operating as MH370) could have been or was taken over remotely as the technology was not implemented on commercial aircraft.”

Seized by a stowaway

Could someone have boarded the aircraft prior to the passengers and crew, either in a suicidal mission or with the intention of landing at, say, Christmas Island, 1,000 miles northwest of Western Australia?

This is a theory that Philip Baum sees as second-most likely after pilot suicide. He has demonstrated that there is an underfloor area just outside the flight deck door which could conceal a person. Such a stowaway could also deactivate the transponder, making the aircraft “disappear”.

There are many cases in aviation of ex-employees with a grudge targeting airlines. It is possible that such an individual was responsible. But there are many arguments against such a scenario, and the probability seems extremely low.

The perpetrator would need to have had access to the aircraft before it was readied for departure from Kuala Lumpur. They would need to have overcome the cabin crew, 227 passengers and two pilots to take over the aircraft. And they would need not to be missed when they disappeared at the same time as MH370.

In addition, it is difficult to come up with a motive. No terrorist group has come up with a serious claim to have taken control of MH370 for political or propaganda purposes.

Only if and when the aircraft is found can these theories be tested.

Read More