[centimeter]

> Airlines buy futures in Jet A or Jet A-1. They have no interest in crude oil

It doesn't matter. Airlines absolutely buy crude futures to hedge against changes in fuel cost. It might be impossible to buy futures in the exact good you need, or it might be too expensive due to illiquidity and slippage.

It's like how beer manufacturers buy aluminum futures even though they almost never take delivery on the futures. They're just going to buy the processed aluminum from their regular processed aluminum supplier, but they can still hedge some of the price changes with the easily available physical aluminum futures.

[CydeWeys]

There are jet fuel futures. If they speculate on crude and then jet fuel itself goes up because e.g. a big jet fuel refinery blew up, they're screwed, because the crude future didn't actually hedge against the specific problem they're facing, and now they have to pay a lot more for jet fuel. Or it could be any other problem that specifically affects jet fuel but not crude in general.

Anyway, as usual, Wikipedia has a relevant article, and it seems that airlines do both: https://en.m.wikipedia.org/wiki/Fuel_hedging