Cold pockets
Please note i'm not a pilot, i've just been following the discussion.
Does anyone know what the recommended minimum OAT is for a Boeing 777 and where the fuel temp sensors are located? There seems to be some suggestions that there might have been a localised region of cold fuel. Presumably for that to happen there would have had to be a preliminary failure of the systems in place to mix the fuel up. If the min rec. OAT for a 777 is colder than -76 (which i'm guessing it is), then there should not have been any concern about even localised regions of cold developing unless there was then a secondary failure of another safety system for warming the fuel.
Which seems a little tentative, none of the system failures have been reported yet, but if it is the case it might explain why it's such a rarity. Presumably, then there would need to be a reason why there was a delay of several hours in the effects of the cold....