Pilots lighting up mid-flight may have caused an Air China plane to drop 6,000 meters (19,000 feet).
The CA106 flight from Hong Kong to Dalian, China went from above 10,000 meters to below 4,000 meters in less than less than nine minutes on Tuesday, according to CNN.
The South China Morning Post reported that the drop triggered the release of oxygen masks from the cabin ceiling. The aircraft landed safely in the northern port city of Dalian in China’s Liaoning province.
One passenger wrote on Weibo, a Chinese social media site:
“The announcement from the cockpit said the ability to increase oxygen in the cabin malfunctioned so the plane lost pressure.”
Multiple Chinese state media outlets have since reported the cockpit crew were smoking and mistook two switches as air recycling fans and turned them off, causing the loss of cabin pressure.
The airline said the crew are being investigated by the Civil Aviation Administration of China (CAAC).
“If the investigation discovers crew behaviors that have violated rules and regulations, we will adopt a zero-tolerance attitude and seriously punish those found responsible,” the airline said in a statement, as per CNN.
“I didn’t think too much of it at the time — we didn’t know what was going on, nor did the flight attendants it seemed,”Hoby Sun, who was a passenger on the plane told CNN.
“I’m not physically hurt, but the psychological impact lingers. When I close my eyes, I see the oxygen masks dangling in front of me.”
News Corp is reporting the airline has cancelled some flights following the incident.