A Singapore Airlines passenger plane dropped 13,000ft after both engines lost power in a huge storm in the South China Sea.
The plane, carrying 194 people, was three and a half hours into its five-hour flight from Singapore to Shanghai when the Rolls-Royce Trent 772 engines failed at 39,000ft.
The pilots restored power by putting the Airbus A330-300 into a controlled descent to 26,000ft before climbing again.
Experts said it was "very unusual" for both engines to lose power.
According to the Independent, the plane's engines "were thoroughly inspected and tested upon arrival in Shanghai with no anomalies detected" and it later returned to Singapore after a two-hour delay.
A Singapore Airlines spokesman told Sky News: "We are not able to provide further information, but we can confirm that the same aircraft was used for the return flight.
Tracking site Flightradar24 tweeted about the loss of power.
According to the Daily Mail, a pilot told Reuters it is extremely rare for a plane to lose power in both engines, but flight crews are trained to handle the event.
The unidentified pilot with a Southeast Asian airline told the news agency: "We do occasionally lose power in one engine for various reasons, but you hardly ever lose both engines.
"If that happens, you follow the procedures in your check-list and try to restart the engines. The pilots successfully did that here."
Singapore Airlines, Rolls Royce, and Airbus are looking into the incident.
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