The likely cause, according to the UK Air Accidents Investigation Branch (AAIB), was ice that had accumulated in the 777’s fuel supply that formed from water that would be present in the fuel anyway.
“Certification requirements, with which the aircraft and engine fuel system had to comply, did not take account of this phenomenon as the risk was unrecognised at that timeâ€Â, the report stressed, explaining that research concerning ice build-up in fuel supplies dated back over 50 years, but the effects of it were only much more recently discovered.