The table below presents the reconciliation of total operating expenses (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. The major components of our total CASM and our total CASM excluding special items and fuel for the years ended December 31, 2018 and 2017 are as follows (amounts may not recalculate due to rounding): Year Ended December 31, Percent Increase (Decrease) 2018 2017 (In cents, except percentage changes) Total CASM: Aircraft fuel and related taxes 2.86 2.22 28.8 Salaries, wages and benefits 4.34 4.32 0.5 Maintenance, materials and repairs 0.73 0.71 2.6 Other rent and landing fees 0.67 0.65 3.1 Aircraft rent 0.45 0.43 3.5 Selling expenses 0.54 0.53 0.9 Depreciation and amortization 0.65 0.62 5.9 Special items, net 0.28 0.26 8.3 Other 1.80 1.78 1.6 Regional expenses: Aircraft fuel and related taxes 0.65 0.50 30.7 Other 1.88 1.87 0.4 Total CASM 14.85 13.88 6.9 Special items, net: Special items, net (0.28) (0.26) 8.3 Regional operating special items, net — (0.01 ) nm  (1) Aircraft fuel and related taxes Aircraft fuel and related taxes - mainline (2.86 ) (2.22 ) 28.8 Aircraft fuel and related taxes - regional (0.65) (0.50) 30.7 Total CASM, excluding special items and fuel 11.06 10.90 1.4 $^{(1)}$ Not meaningful. Significant changes in the components of total CASM are as follows: • Aircraft fuel and related taxes per ASM increased 28.8% primarily due to a 29.1% increase in the average price per gallon of fuel to $2.21 in 2018 from $1.71 in 2017, as well as a 1.8% increase in gallons of fuel consumed. • Depreciation and amortization per ASM increased 5.9% due in part to our fleet renewal program, as we took delivery of eight owned mainline aircraft in 2018. The continued rollout of Premium Economy and harmonization of seating configurations across our fleet as well as information technology and software development projects associated with our merger integration also drove higher depreciation and amortization expense. • Regional aircraft fuel and related taxes per ASM increased 30.7% primarily due to a 28.3% increase in the average price per gallon of fuel to $2.30 in 2018 from $1.79 in 2017 as well as a 4.0% increase in gallons of fuel consumed. 53