AN investigation has been launched after an Air China jet plummeted over 20,000ft when smoke from a pilot's e-cigarette entered the cabin.
Civil Aviation Administration of China (CAAC) said in a news conference that a co-pilot accidentally turned off air conditioning system while trying to turn off air recycling fans to prevent the vapor from spreading into the passenger cabin.
Instead, the wingman accidentally triggered a drop in oxygen levels, prompting an altitude warning that caused the almost fatal plunge - from 32,800 to 13,100 feet in less than nine minutes, Civil Aviation Administration of China officials told the station.More news: Ban on import of Israeli goods moves step closer
In reaction to an alarm triggered by the air conditioning shut off, the flight crew dropped the plane's emergency oxygen masks and initiated a descent to a lower altitude with breathable air.
After the sudden descent to 10,000 feet (approx 3,000 metres), the plane thankfully recovered when it managed to climb back to 26,000 feet (approx 7,900 metres) and ended up arriving safely in Dalian.
"China News" said the co-pilot had shut off the air conditioning units.
The flight went on to land in Dalian without incident, but officials are reportedly investigating the incident "in greater detail", reviewing the flight data recorder and the cockpit voice recorder for more information.More news: Congress to Trump: Cancel Putin summit after new Mueller indictments
CAAC official Qiao Yibin said "severe punishment" will be handed "in accordance with laws and regulations", as reported by CNN.
Air China's website says smoking is strictly prohibited on all its flights. The national carrier said that, if the allegations about its crew smoking were true, it would deal with them with "zero tolerance".
"[We] didn't know what was going on, nor did the flight attendants, it seemed", said Hoby Sun, a passenger on flight CA106.
The smoking of e-cigarettes, like proper cigarettes, is banned on Air China flights.More news: 'Unprecedented Level of Animus!' Strzok Gets His Smackdown for Anti-Trump Bias