I have never seen an airline that breaks down costs to a per airplane cost. It is easy enough to get a fleet average cost for fuel, maintenance and crew, but things get confusing when you add overhead such as operations, management, reservations & airport staff, engineering and other fixed costs such as building rent, IT
, finance costs, etc. Airlines are large companies and there is a lot of money spent supporting the airplanes that is not tied to any specific plane. Airlines usually break costs down by category such as wages 40%, fuel 30%, Maintenance 10%, etc.
If you have never designed an airplane part before, let the real designers do the work!