So how actual airlines work are with aircraft grouped into subfleets. Each subfleet is generally based on types, but maybe 1 subfleet for all CRJ with the stairs, and another subfleet for without. Now, these fares and expenses are attached to a subfleet. So someone can go into as much detail as they want - just a single subfleet for all aircraft, no matter the type, or let's say 10 different subfleets with varying fares and expenses.
Schedules are also attached to subfleets, so you can dictate that flight from airport X to Y is assigned the subfleet for the CRJ with stairs.
Ground handling, etc, will be based on a general landing fee, I think. These can also differ by airport, but I think the way I'm going to do it is by some modifier. I haven't thought it through yet, but there might be a few different expense types that you can assign to the subfleet. Landing fees are generally done by weight, and I believe they can include ground handling.
I'm still trying to figure out the best way for these. It gets pretty complicated very fast Maybe a price per 5-tonnes or something at the airport level. I have to see how this is actually charged and handled.