BEIJING- Chinese authorities have launched an investigation to determine why a plane was forced to drop more than 6,000m due to the loss of cabin pressure.
The Air China flight from Hong Kong to Dalian dropped 6,500 below the cruising altitude and oxygen masks dropped in the cabin.
Local media speculates the crew was smoking in the cockpit and somehow mishandles the ventilation system.
Aviation authorities in China are listening to flight data recorder and cockpit voice recorder to understand what happened.
If a plane loses cabin pressure, the pilot has to bring the aircraft to a lower altitude to keep crew and passengers safe.