: An emergency descent by an Air China aircraft after cabin oxygen levels dropped has been linked to a co-pilot smoking an e-cigarette during the flight, according to China's aviation regulator.
The state-owned Air China Boeing B737 aircraft was flying to the Chinese city of Dalian from when it dropped to 10,000ft, with oxygen masks deployed. It then climbed again to continue to its destination.
Chinese airlines have a good safety record, but passengers have accused pilots of smoking during flights, although few such incidents have been confirmed.
"In the preliminary investigation, the co-pilot was found to be smoking an e-cigarette," state-owned "China News" said, citing the Civil Aviation Administration of China (CAAC), who are investigating the incident.
"Smoke diffused into the passenger cabin and relevant air conditioning components were wrongly shut off, without notifying the captain, which resulted in insufficient oxygen," it quoted the regulator as saying.
The official said the shut-off triggered an alarm, prompting the crew to perform an emergency pressure-relief procedure, which released the cabin's oxygen masks.
The crew realised the problem after the descent and restored the air conditioning, allowing cabin pressure to return to normal, he said.
Air China said it would terminate the contracts of the employees involved in the emergency descent incident, and suggested the CAAC cancel their licences, it said on its official account on China's Twitter-like Weibo. Air China also said in a previous Weibo post it had a "zero tolerance" approach towards wrongdoing by any crew.
The incident featured heavily on Chinese social media, with some commentators demanding harsh punishment and revocation of the pilot's flight licence.
China's aviation regulations, which bar flight crew from "smoking on all phases of operation", also banned passengers from using e-cigarettes on flights in 2006.