That's direct fuel cost. *The non-fuel costs are also driven by the price of fuel - but indirectly as pass thru.

OK - so the Pawnee D does not have the STC - what about all the
earlier models made 20 years or so prior? The bulk of the fleet I'd
wager.

Insurance, maintenance, and hanger rent driven proportionaly by fuel
cost? I doubt that. Show me the numbers!