A policeman takes a nap beside a board written with messages for passengers onboard the missing Flight MH370 in Beijing
A policeman takes a nap beside a board written with messages for passengers onboard the missing Malaysia Airlines Flight MH370 during a closed meeting held between Malaysian representatives and Chinese relatives of passengers on Flight MH370 at Lido Hotel in Beijing May 2, 2014. REUTERS/Jason Lee

Passengers on Malaysia Airlines Flight 370 may have died from lack of oxygen hours before the pilot allegedly performed a "controlled ditching" and crashed the plane in the Indian Ocean. The new book, The Truth Behind the Loss of Flight 370, contains the theory of expert aircraft accident investigator and book author Ewan Wilson.

Wilson, a commercial pilot and Kiwi Airlines founder, believes the 239 people on board became unconscious four hours before the Malaysian aircraft went down in the ocean. He said his conclusion was based on his evaluation of "every conceivable alternative scenario."

The author claimed that aviation investigators have considered the possibility of MH370 pilot Captain Ahmad Shah intentionally depressurizing the cabin so passengers will be starved of oxygen. In this scenario, oxygen masks would have immediately dropped down so passengers can get oxygen supply. However, investigators said the supply usually lasts for only 20 minutes and passengers who failed to reach for their masks because they were asleep would have lost consciousness in a matter of minutes.

Wilson claimed that everyone on board MH370 would have "slipped into a coma and died" from lack of oxygen supply.

The author explained his theory in the book and claimed Ahmad Shah could have locked his co-pilot out of the cockpit to execute his plan. He was alleged to have performed a "controlled ditching" which would explain why no plane debris was found after months of searching. The author believes MH370 was intact when it landed and sank in water.

The Australian Transport Safety Bureau (ATSB) has concluded that people on board MH370 may have died from hypoxia or deficiency of oxygen. Malaysian authorities had also suspected the crash to be an "inside job" involving Ahmad Shah. However, Australian authorities did not have new evidence from the Malaysian aircraft.

The MH370 claims were published in the book Wilson co-wrote with New Zealand journalist Geoff Taylor. Wilson, a veteran aviation safety investigator, said he wanted to "convey the human stories" of the missing plane.

Wilson and Taylor believe Shah was reportedly suffering from a mental illness. They claimed Sha deceived Fariq Hamid, the co-pilot, into taking a break 40 minutes after the plane took off from Kuala Lumpur to Beijing.

The authors claimed Sha made his last known contact with air traffic control after locking out Hamid with the words, "Goodnight Malaysian 370" before switching all communications. Wilson and Taylor believe Sha had enough time to carry out his "final act" during the last remaining hours' worth of oxygen.

The authors conclude the pilot had then directed the plane to head towards the southern Indian Ocean. After the fuel ran out, he let the plane cruise a further 100 nautical miles before his controlled ditching act.

Wilson said Sha was known for his methodical, technical and egotistical nature. He believes the pilot may have issued a challenge to his family and the world to find the plane.