Over three months have passed since Malaysia Airlines Flight 370 disappeared over the Indian Ocean, setting off an international search effort and raising serious concerns over air safety around the world.
But on Thursday, an official report from the Australian Transport Safety Board (ATSB) theorized it was a lack of cabin pressure, not the work of Iranian hijackers, that ultimately brought down the Boeing 777 and killed 239 passengers and crew.
The 55-page report details how investigators reached these conclusions after comparing the conditions on the flight with previous disasters - despite a lack of any new evidence from debris of the jetliner itself.
According to the report, the plane most likely crashed on the coast of small islands in the Indian Ocean while on autopilot, after the crew was incapacitated by oxygen deprivation (hypoxia). Previous hypoxia-linked disasters show similar circumstances to MH370: a lack of communications, a steady flight path, and the potential for a lack of discernible debris.
"Given these observations, the final stages of the unresponsive crew/hypoxia event type appeared to best fit the available evidence for the final period of MH370's flight when it was heading in a generally southerly direction," the ATSB report said.
Past history, MH370 present?
Earlier ATSB reports pointed to fuel starvation as the cause of the crash, pointing to the location of "pings" from the plane's transponder last recorded several hours after the flight deviated from its flight path.
One air crash commonly compared to the circumstances behind MH370 is Helios Airways Flight 522, which crashed due to a combination of hypoxia and fuel starvation in 2005.
Helios Airways Flight 522 crashed on August 14, 2005 after several hours of "flying blind." Passengers and crew succumbed to oxygen deprivation during the short flight from Athens to Lanarca due to a problem with air pressurization.
A flight attendant, the last person to succumb to hypoxia, placed the aircraft in a holding pattern for several hours while he tried unsuccessfully to land the plane.
Greek authorities were only alerted to the tragedy, however, after numerous attempts at audio contact were established - causing several F-16s to be dispatched to establish visual contact with the plane. Only then did they see that the crew was slumped over, motionless, with oxygen masks hanging in the cabin. The plane later crashed at high speeds into a mountainside due to fuel starvation.
If the Malaysia Airlines flight faced similar circumstances, a rescue attempt - and the possibility of notifying local authorities over international waters - may have been impossible from the depths of the Indian Ocean.
The search braves on
Thursday's report also pointed to a crash site much farther south into the Indian Ocean than previously thought, officials said, citing the possibility that the plane flew on a steady flight path for hours after the crew became incapacitated.
The finding has prompted Australian authorities to move the search area farther south, extending what is already the most expensive search for a flight in aviation history.
The next phase of the search is expected to start in August, covering some 60,000 sq km at a cost of 60 million Australian dollars ($56 million) or more, according to Reuters.
The new priority search area is around 2,000 km west of Perth, Australia - over a stretch of isolated ocean frequently lashed by strong winds and massive swells.