Astonishing new theory about MH370 mystery suggests pilot was actually a 'hero'.

Experts have posed dozens of theories about what led to the downing of MH370 on March 8, 2014, causing the deaths of 239 people.

But the latest frames the pilot in an entirely different light: as a hero.

Australian aviation expert Michael Gilbert spent 18 investigating the mystery disappearance of the Malaysian Airlines plane and concluded it is likely that the windshield caught fire mid-flight, knocking out communications and navigation – essentially leaving pilot, Zaharie Ahmad Shah, flying blind towards Penang.

“I believe that the pilot then elected to do what many pilots in stricken planes had done in the past – steer it clear of populated areas,” Gilbert wrote.

In this case, that meant “straight down” into the Indian ocean.

Gilbert examined maintenance records and flight history of the aircraft to back up his theory that a faulty windshield heater sparked a blaze in the cockpit.

“The pilot would have realised there was no reasonable chance of manually flying the plane,” he wrote.

“There were no instruments, it was night, there was no moon, he could only occupy the cockpit for short periods of time and oxygen supplies were dwindling.”

Gilbert proposes that after Shah set the suicidal course, the plane ultimately ran out of fuel and came down roughly 200km outside the area currently being searched by authorities.

Long-held theories about a deliberate ‘death dive’ were given credence last month following analysis of a portion of MH370’s wing flap found off the Tanzanian coast in September.

According to the Australian Transport Safety Bureau, it showed the plane had not been prepared for landing. The bureau also noted that final communications with the plane showed it in an “increasing rate of descent”.

Other theories centred on rumours that Shah had recently ended a relationship with a married woman, and had previously simulated the selected route.