I also use the "Aircraft" mod (https://mods.factorio.com/mod/Aircraft), and although I manage to use oil barrels as fuel, the spent fuel slot was not added on those vehicles and no empty barrels appear after the oil is consumed.
Is it possible to integrate this mod with "Aircrafts"? Or do I need to ask the maintainer of this other mod?

Thanks.

Just read through code of "Aircraft". There are not any line of fuel_category = "chemical" in their burner definitions, causing my code to skip such entities.
The solution is to add the line fuel_category = "chemical" into those burner definitions, in Aircraft/prototypes/entities.lua.

PS: Although the fuel_category has default value "chemical" if it is not set, my code has to handle other entity types as well. This means that the actual burner can either be burner or energy_source properties, and my code has to handle both. So checking fuel_category == "chemical" is needed as the only reliable condition.

I have pulled the code merge request (#47),
but I am not sure when that will be made into an update, as it seems its mod author is not active at the moment.

I modified the "Aircraft" mod locally on my machine for now.
Good mod anyway.

Thanks.