Current planes supply usage is:
1 point for combat mission
1/3rd point for short, or semi-combat mission (CAP, recon etc.)
bombload/1000 for bombers using bombs
It generally seems, that supply usage represents only used ammunition, not fuel.
Since 1 point of supply is equal roughly to 1 ton, upon closer examination:
B-17 takes 1700 gallons of fuel, it should use extra 6 points of supply for longer range mission
B-29 takes 8168 gallons, that gives 30 (!) extra supply, plus probably 2 points for MGs ammo. Try to base them in China now! One plane-strike-mission -50 supply
P-38 take 300-400 gallons, so 1.2-1.5 extra supply
For Japan:
A6M3a 570 litres (5.7 extra supply)
Dinah II 1490 litres (1.5 supply)
Betty 3640 litres (3.64 supply), and 6490 litres (6.49 supply) for G4M2 model
That would need introducing one code line, with smart formula, based probably on plane Durability, number of Engines, range and type.
Or simple overall calculation based on difference between maximum, and initial takeoff weight.








