Up in smoke

An Air China jet made a rapid emergency descent after a co-pilot mistakenly turned off air-conditioning systems in a bid to conceal his e-cigarette smoke, Chinese media quoted the country's civil aviation authority as saying yesterday.

The incident, which resulted in the deployment of passenger oxygen masks, occurred Tuesday on a flight by the Chinese flag carrier from Hong Kong to the city of Dalian in northeastern China.

The Civil Aviation Administration of China (CAAC) said in a press conference in Beijing that the drama was triggered when the co-pilot sought to turn off a ventilation system to prevent his smoke spreading into the main cabin, the respected news site Caixin said.

Smoking is not allowed aboard Chinese commercial passenger flights.

But the co-pilot accidentally switched off air-conditioning instead, leading to a decrease in cabin oxygen levels.

That set off an emergency warning system indicating that the 737 jet may have flown too high and instructing the pilots to quickly descend.