Canadian investigators have disclosed that a Korea-bound Delta Air Lines Airbus A350-900 encountered engine surges and a thrust roll-back before the aircraft diverted to Alaska.
The aircraft (N508DN) had been operating the DL159 service from Detroit to Seoul on 21 January.
Transportation Safety Board of Canada says the right-hand Rolls-Royce Trent XWB powerplant began experiencing surging which, it says, led to the roll-back and subsequent shutdown.
The aircraft was 735nm north-north-west of Yellowknife, according to the board, which would put it in the area of the Beaufort Sea.
It times the incident at 15:30MST which would have been about 5h after departure. The aircraft diverted to Fairbanks in Alaska, where it landed some 2h 15min later, at around 15:45 local time.
US FAA regulators approved the A350-900 for 300min extended twin-engined operations in 2016, and subsequently increased this to 370min..
The board says the aircraft landed without further incident, and none of the 189 occupants was injured.
But it has not given any indication as to the cause of the surging in the powerplant.
Delta Air Lines took delivery of the aircraft in March 2018, according to Cirium fleets data.