EgyptAir Flight 804 Disaster Caused by Pilot Smoking

The cause of the air disaster had been a mystery, but in examining the evidence, BEA investigators were able to piece together a picture of the final minutes of the flight. Their conclusion was that a cigarette the first officer was smoking started a fire that was fed by a supply of aviator's oxygen being emitted by one of the emergency oxygen masks. The report said that a maintenance tech might have left the oxygen supply to that mask turned on, but it is standard pre-flight procedure in every pressurized airplane to check the emergency masks and ensure that they are off before takeoff.

The fire theory is not a new one. As early as 2018, investigators were pointing to a flight-deck fire as the cause of the crash. It wasn't until they pieced all the parts together that they were able to pin down the source of the fire. Key to the finding was the plane's cockpit voice recorder, which captured a hissing sound in the background that turned out to be oxygen leaking from a mask.

EgyptAir no longer allows smoking by their crews aboard any of their aircraft.