Boeing 777 pilot: Autopilot theory for missing plane makes the most sense

(CNN) – One theory gaining credence among experts is that a disturbance, such as a fire, happened on board missing Malaysia Airlines Flight 370 that disabled the pilots and knocked out electrical systems, but also allowed the plane to continue flying on autopilot. Without anyone manning the controls, it continued to fly until it ran out of fuel.

"It's a very viable theory. It's something that I've been touting that seems the most plausible all along," aviation analyst and Boeing 777 pilot Les Abend tells CNN.

Abends says a "smoldering fire that created smoke" would have prompted the crew to don oxygen masks, which unfortunately cannot completely seal out smoke and toxins.

"The captain realized it was compelling enough to get the airplane turned, entered a waypoint that was an alternate airport in the flight management computer, and kept the autopilot connected ... to reduce workload," said Abend.

"As it progressed towards the waypoint, the toxic fumes perhaps overcame the crew and perhaps the passengers, and at some point they were no longer able to function," said Abend.

For more from aviation analyst Les Abend, check out the video above.