Air China flight from Hong Kong to Dalian drops 25,000 feet in 10 minutes after loss of cabin pressure

An Air China plane that departed Hong Kong for Dalian on Tuesday night dropped 25,000 feet in 10 minutes, triggering the release of oxygen masks from the cabin ceiling, though the aircraft later landed safely in the northern city, flight data indicated.

At least two passengers posted photos on social media showing those aboard flight CA106 wearing masks but looking calm.

One writing on Chinese microblogging platform Weibo said: “The announcement from the cockpit said the ability to increase oxygen in the cabin malfunctioned so the plane lost pressure.”

According to tracking website FlightRadar24, the 159-seater Boeing 737 suddenly began descending at 7.40pm between Shantou and Xiamen, half an hour after it took off from Hong Kong International Airport.

Similar data from aviation company Flight Aware indicated an initial drop of 14,100 feet in four and a half minutes, from 35,000 feet to about 10,000, at which point the aircraft levelled off and began climbing to cruising altitude soon after.

The Weibo user posted a photo of himself in a mask and giving a thumbs-up sign, saying the issue had been resolved as the plane approached Xiamen.

The aircraft then continued to the port city of Dalian in China’s Liaoning province, with the flight lasting three and a half hours.

Air China and Hong Kong’s Civil Aviation Department have been contacted for comment about what happened. No reports of injuries have surfaced.

A professional pilot with more than 25 years of experience said any depressurisation of the cabin would prompt the pilots to descend to 10,000 feet, as they did in this case.

“That is what is considered a safe, breathable atmosphere for the passengers, and then the captain has to make a decision,” he said.

“I would say in just about every case, you would want to land as soon as possible. But it depends on what happens in the plane and what the pilots’ checklist says.

“In most cases you would have declared an emergency on the way down and then you would have landed at the most suitable airport.”

The Boeing plane used for CA106 is registered as B-5851 and is four years old.

Hong Kong’s Cathay Pacific Airways has an 18.13 per cent stake in Air China, the national flag carrier. Air China holds a 30 per cent stake in the city’s flagship airline.

Air China and its sister airlines operate a fleet of 655 aircraft, according to the company’s 2017 annual report.

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