Kerosene, unfortunately it is difficult to define struck work in ACMI. Let's assume that SAI (just for the sake of the example) has an ACMI contract with Asiana for instance. Asiana goes on strike, SAI continues flying the contract and actually now adds a few frequencies. Asiana pilots not very happy obviously but nothing they can do because the govt could care less. Let's say now that SAI goes on strike, Asiana still needs to move their freight, they advise SAI that their contract is cancelled because they cannot fulfill their contractual obligations and they sign a contract with let's say Tradewinds or Focus or both (again just as an example). The latter have not crossed the line, it is Asiana's freight they are carrying, not SAI's....
Another example is the military. If PO goes on strike the military will turn to someone else for the lift and whoever does fly it is not crossing the line, it's not PO freight. Now if someone were to fly PO flt #s on PO scheduled runs, then yes, that is PO freight.