Smoking pilot causes flight chaos
A co-pilot smoking an e-cigarette on an Air China flight caused the plane to start a rapid emergency descent, according to investigators.
They say he tried to hide the fact that he was smoking but accidentally shut off the air-conditioning, causing oxygen levels to fall.
The crew on Tuesday's flight from Hong Kong to the city of Dalian released oxygen masks and brought the plane more than 6500m lower.
It later returned to cruising altitude.
An initial probe by China's Civil Aviation Administration in China has shown that the co-pilot tried to turn off a fan to stop smoke reaching the passenger cabin without telling the captain, but turned off the air-conditioning unit instead.
Passengers say they were told to fasten their seat belts as the plane had to descend.
The BBC reported that the regulator's safety officer Qiao Yibin said the crew had to perform emergency measures, dropping oxygen masks until they could figure out the problem.
The airline promised a "zero-tolerance" approach to crew misbehaviour on Chinese social media site Weibo.
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