A senior official from the Civil Aviation Administration of China (CAAC) told reporters Friday that, without notifying the pilot, the unnamed co-pilot was trying to turn off air recycling fans to prevent the vapor from spreading into the passenger cabin.
Instead, he toggled the wrong switches, which were close to his intended target, leading to a drop in oxygen levels that triggered altitude warnings.
Qiao Yibin, the CAAC official, promised to hand down "severe punishment in accordance with laws and regulations," if the regulator's final conclusion on the incident matches its initial finding.
Air China fired the entire flight deck crew and suggested CAAC revoke their pilot's licenses upon completing its investigation, the country's flag carrier said Friday night in a statement.
Air China flight CA106, en route from Hong Kong to the northeastern Chinese city of Dalian, descended from above 10,000 meters (32,800 feet) to below 4,000 meters (13,100 feet) in less than nine minutes Tuesday shortly after it reached cruising altitude, according to phone GPS data shared with CNN by a passenger on board.
The Boeing 737 jetliner was carrying 153 passengers and nine crew members on the three-hour journey and landed safely in Dalian, CAAC said Thursday.
Citing anonymous industry sources, multiple Chinese state media outlets had reported earlier that, after the abrupt drop in altitude, the plane eventually climbed back to around 7,500 meters (24,600 feet) and flew to its destinat