Probe after Singapore Airlines flight loses power in both engines at 39,000 feet over Hong Kong

After a Singapore Airlines plane carrying 194 people lost power in both engines outside Hong Kong on Saturday, plummeting almost four kilometres before pilots regained control, the airline said it was still working to determine the cause of the incident.

The drama on the Shanghai-bound Airbus A330 unfolded some 3½ hours after its 5.35pm departure from Singapore when, over a period of 30 minutes, the plane descended from about 11,900 metres as the first engine failed, followed by the second. Pilots managed to regain full control of the plane at 7,900 metres as both Rolls Royce engines regained power.

The airline said it had begun a joint investigation with Airbus and its engine supplier Rolls Royce into what caused flight SQ836 to lose power.

Singapore Airlines confirmed the incident on Tuesday evening, revealing that the pilots put the plane into a deliberate descent in order to regain power in one of the failed engines.

The Aviation Herald, an online clearing house for airborne incident reports, first reported the engine failure on Tuesday morning.

"Both engines experienced a temporary loss of power, although one engine returned to normal operations almost immediately," the airline said in a statement. "The pilots followed operational procedures to restore normal operation of the second engine by putting the aircraft into a controlled descent."

The plane landed in Shanghai at 10.56pm, where "the engines were thoroughly inspected and tested … with no anomalies detected", the airline said.