As Flight 780 neared Hong Kong, the crew were unable to change the thrust output of the engines.

[2][3] The cause of the accident was contamination of the fuel taken on board at Surabaya, which gradually damaged both engines of the aircraft.

[5] The flight's two Australian pilots, Captain Malcolm Waters and First Officer David Hayhoe, who safely landed the aircraft despite the extraordinary challenge, have been compared to pilots Chesley Sullenberger and Jeffrey Skiles of US Airways Flight 1549 the previous year (January 2009).

The aircraft involved was an Airbus A330-342, registered as B-HLL with serial number 244, fitted with two Rolls-Royce Trent 772-60 engines.

The aircraft was withdrawn from service on 13 August 2020, at the expiration of its lease, after its last commercial flight from Beijing to Hong Kong as KA993.

Cathay Pacific Flight 780 departed from stand 8 at Juanda International Airport in Indonesia.

[3] Almost two hours after departure, at 03:16 UTC, the "ENG 2 CTL SYS FAULT" ECAM message reappeared.

After another two hours elapsed, the aircraft was on descent to Hong Kong when, at 05:19 UTC, about 203 kilometres (126 mi; 110 nmi) southeast of Hong Kong International Airport, the aircraft's ECAM displayed "ENG 1 CTL SYS FAULT" and "ENG 2 STALL" within a short period.

Following these actions, the crew declared a "pan-pan" with Hong Kong air traffic control, requesting the shortest possible route to the airport and priority landing.

[3] A few minutes later, about 83 km (52 mi; 45 nmi) southeast of Hong Kong International Airport, the aircraft was in a descent and approaching an altitude of 8,000 ft (2,438 m) when an "ENG 1 STALL" ECAM message appeared.

2 engine remained running below idle speed, about 17% N1, providing sufficient thrust to level off at 5,500 ft and reach Hong Kong.

The valves were found to be stuck in positions corresponding to the recorded thrust output of each engine as it approached Hong Kong.

The investigation discovered that not all procedures had been followed when the system was brought back into service,[1] and that salt water had inadvertently entered the fuel supply.

The presence of salt water compromised the filter monitors in the pipeline system, releasing the SAP particles into the fuel.

[10] The accident was featured in the first episode of season 19 of the Canadian TV series Mayday labeled "Deadly Descent".