Air China pilots fired for mistake that plunged flight 25,000 feet

July 13 (UPI) -- Air China announced Friday it will fire the pilots of a flight that plunged 25,000 feet this week, after it was found human error caused the plane to plummet.

Flight 106 was headed from Hong Kong to Dalian, China, Tuesday night when it lost the altitude over a span of just 10 minutes. The fall was severe enough the automated flight systems deployed oxygen masks.

The Civil Aviation Administration of China determined the co-pilot had smoked an electronic cigarette and, without telling the chief pilot, tried to turn off a circulation fan to keep the vapor out of the passenger cabin -- but switched off the air conditioning instead.

"[The co-pilot] mistakenly switched off the air-conditioning unit that was next to it, resulting in insufficient oxygen in the cabin and an altitude warning," said CAAC investigator Qiao Yibin.

If a plane loses cabin pressure, it must fly at a lower altitude to give crew and passengers breathable air. Once the pilots saw the air conditioning was off, they turned it back on and regained altitude.

Flight 106, with 162 passengers and crew, landed safely in Dalian.

Aviation experts are critical of the pilot's decision to continue the flight, since the oxygen masks had been activated -- meaning they'd be unavailable in the event of a second emergency.

The carrier also recommended the CAAC revoke the pilots' licenses.