On 12 September 2021, a Boeing 777-300 in the cruise at FL 380 and approaching Oman from the east at night experienced a sudden left engine failure. It was shut down, a PAN call was made and diversion to Muscat made in preference to completing the intended flight to Abu Dhabi. An off-wing examination of the GE90 engine which failed found that the hydro-mechanical unit of the accessory gearbox had malfunctioned in a way which allowed fuel to mix with the engine oil. This failure had not been anticipated in the applicable Fault Identification Manual which was amended accordingly.