First Officer Fariq Abdul Hamid would have then taken over, and Kuala Lumpur controllers signaled the plane's handoff to Ho Chi Minh City controllers, and Fariq Abdul Hamid replied "Good night. Malaysian 370."
It's the last anyone would hear from either of the pilots.
Negroni, an aviation journalist who covered the plane's doomed trajectory for ABC News, theorises that at that point something massive happened to the plane's cabin pressure system, and it rapidly decompressed, sucking out all the oxygen.
Investigators have since found no evidence of sabotage or terrorism or that either of the pilots were suicidal.
She says the facts all point more towards a cabin decompression disaster.
Because humans can't breathe at 35,000 feet, cabins are filled with an air pressure level consistent with 8,000 feet, according to the Post.
But if something happens to that pressure - and that could have been sparked by anything from structural flaws to problems with the doors' seals - the human brain's ability to think is rapidly and massively compromised.
Negroni surmises that the copilot faced another problem - an issue with the cabin's oxygen system, so even with an oxygen mask, he would have been in trouble and not able to think properly and his arms would have started to jerk spasmodically.
This is why Negroni thinks that the plane was switched to "standby" instead of putting out a mayday call - explaining why the transponder signal stopped and controllers could still see the airplane on radar but couldn't determine its altitude.
Additionally, someone was still flying the plane - and flying it on a bizarre course, turning southwest, then north, then south. Negroni thinks that was the copilot, overcome with oxygen deprivation, was at the controls.
'"I think he was no longer doing much reasoning, because his ability to do that was long gone,' Negroni said.
"When you consider how muddled Fariq's mind must have been, you can see many ways in which MH-370's bizarre flight path can be explained," she wrote.
The plane then flew hours more, likely on autopilot, and vanished.
The journalist feels that the younger pilot, who was only 27 and had much less flying time than the captain, was too inexperienced to handle such a massive plane failure, but that Zaharie, 53, a 33-year veteran of the airline with 18,000 hours under his belt, may have been able to save the plane.
Captain Zaharie Ahmad Shah, however, could have been in the bathroom. While an oxygen mask would have dropped, the disoriented pilot would have had to have taken it off to reach the cockpit, and that would have been enough time to render him useless to help.
