Why airlines use KG for fuel instead of liters/gallons?
 

I remember reading this a while ago, but can only remember something to do with temperature or specific gravity.
Can't really remember.

Please someone explain?

I seem to remember reading it's to do with fuel volume increasing/decreasing with temperature. Therefore loading 100 gals/ltrs of fuel will give you different volumes at different temperatures, whereas loading 100KGs will always give you the same amount for the purposes of calculating range/duration etc. (although the volume of 100KGs worth of fuel will vary with temp). I'm in no way shape or form an expert so stand to be corrected if that isn't the case :ok:

The warmer the fuel is the less dense it is. 1Kg of fuel always has the same calorific value in terms of energy but it may take up a larger volume if it is less dense. Not such a big deal in a car for instance where you will get small variations based on 50l of diesel but very much a problem when you're burning a few thousand kilos of fuel.

Hence kilos and not litres.

Jet fuel comes out of the refining process at different specific gravities, also. That is, at the same temp, different loads of Jet A might weigh differently even at the same temp and volume.