In a Google+ post, Chris Goodfellow argued that smoke filled the cockpit, maybe from a burning tire on the front landing gear.
The pilots turned the plane toward an airport that could handle the 777, turned off the transponder along with other electronics in an effort to isolate the source of the fire, and were then overcome by smoke, he theorized.
The plane's autopilot kept the course until it ran out of fuel and crashed hours later.
Goodfellow's theory is appealing, we noted, because it fits the facts we have on MH370. It impressed The Atlantic's James Fallows, himself a pilot: "His explanation makes better sense than anything else I've heard so far ... It's one of the few that make me think, Yes, I could see things happening that way."
Other pilots aren't convinced, though. In an interview with Business Insider, Michael G. Fortune, a retired pilot who now works as an aviation consultant and expert witness, said pilots preparing to change destination "would have communicated their emergency and intentions to turn around, as well as ask for assistance and direct routing to a suitable airport from the air traffic controllers very quickly."
Goodfellow also wrote: "in the case of fire the first response if [sic] to pull all the main busses and restore circuits one by one until you have isolated the bad one."
Fortune, who flew 777-200ERs like the one involved here, said pilots follow a specific procedure when there's smoke or fire in the cabin. He didn't buy into the idea that the transponders would have been turned off in an attempt to deal with the problem. "The checklist I utilized for smoke and fumes in the B-777-200ER does not specifically address the transponder being turned off," he said.
Steve Abdu, a 777 captain for a major carrier, echoed Fortune's point that there's a clear checklist to follow in this kind of situation. And, he pointed out, it's unlikely smoke would have knocked the pilots unconscious or killed them - because they have oxygen masks.
Each pilot has a quick donning mask, and putting it on is step one on the fire checklist. It covers the full face, even if the pilot wears glasses, and can be put on in about two seconds. "These masks are quite excellent at protecting a pilot from smoke and fumes," Fortune said.
The masks are pretty impressive: Pressing clips on the face part inflates the harness, letting go deflates it. You can see how an example works in this Airbus instructional video: