Additionally, the table below presents the reconciliation of total operating costs (GAAP measure) to total operating costs excluding special items and fuel (non-GAAP measure). Management uses total operating costs excluding special items and fuel to evaluate our current operating performance and for period-to-period comparisons. The price of fuel, over which we have no control, impacts the comparability of period-to-period financial performance. The adjustment to exclude aircraft fuel and special items allows management an additional tool to understand and analyze our non-fuel costs and core operating performance. Amounts may not recalculate due to rounding. $^{(1)}$  See Note 2 to AAG’s Consolidated Financial Statements in Part II, Item 8A for further information on special items. 46 Year Ended December 31, 2018 2017 2016 Reconciliation of Total Operating Costs per Available Seat Mile (CASM) Excluding Special Items and Fuel: (In millions) Total operating expenses - GAAP $ 41,885 $ 38,391 $ 35,082 Special items $^{(1)}$: Special items, net (787 ) (712 ) (709 ) Regional operating special items, net (6) (22) (14) Fuel: Aircraft fuel and related taxes - mainline (8,053) (6,128) (5,071) Aircraft fuel and related taxes - regional (1,843 ) (1,382 ) (1,109 ) Total operating expenses, excluding special items and fuel $ 31,196 $ 30,147 $ 28,179 (In millions) Total Available Seat Miles (ASM) 282,054 276,493 273,410 (In cents) Total operating CASM 14.85 13.88 12.83 Special items per ASM $^{(1)}$: Special items, net (0.28) (0.26) (0.26) Regional operating special items, net — (0.01 ) (0.01 ) Fuel per ASM: Aircraft fuel and related taxes - mainline (2.86 ) (2.22 ) (1.85 ) Aircraft fuel and related taxes - regional (0.65) (0.50) (0.41) Total CASM, excluding special items and fuel 11.06 10.90 10.31