Operating Expenses
Aircraft Fuel. Aircraft fuel expense decreased by $31,287, or 56%, to $24,274 for the three months ended March 31, 2021, as compared to $55,561 for the three months ended March 31, 2020. The decrease was largely driven by a $24,422 change in the mark-to-market gains/losses from our fuel derivative contracts, consisting of a $2,386 gain in the three months ended March 31, 2021 compared to a $22,036 loss in the three months ended March 31, 2020. The decrease was further driven by a 25% decrease in fuel gallons consumed, due to our decreased level of operations as a result of reduced demand relating to the COVID-19 pandemic, as demonstrated by a 20% decrease in passenger service block hours. Partially offsetting these decreases was a 5% increase in the average price per gallon of fuel.
Salaries, Wages and Benefits. Salaries, wages and benefits expense increased by $5,984, or 16%, to $44,075 for the three months ended March 31, 2021, as compared to $38,091 for the three months ended March 31, 2020. A portion of the increase was primarily due to insourcing MSP ground handling operations in April 2020, resulting in approximately $1,200 in higher salaries, wages and benefits, along with increased pilot pay and per diems to support operations under the ATSA. Since the probability of partial vesting was triggered by our IPO, we expensed $2,496 for our performance-based stock options for the three months ended March 31, 2021. No expense was recorded in the three months ended March 31, 2020 for performance-based stock options. Our cargo segment was responsible for $11,236 of the consolidated salaries, wages, and benefits expense for the three months ended March 31, 2021, and was driven by headcount required to support the operations and aircraft under the ATSA.
Aircraft Rent. Aircraft rent expense decreased by $5,433, or 49%, to $5,599 for the three months ended March 31, 2021, as compared to $11,032 for the three months ended March 31, 2020. Aircraft rent expense decreased primarily due to the composition of our aircraft fleet shifting from aircraft under operating leases (for which expense is recorded within aircraft rent) to owned aircraft. Specifically, in the year ended December 31, 2020 we purchased two aircraft previously under operating lease and leased two fewer seasonal aircraft. In addition, in late Q1 2021, we purchased five aircraft previously under operating lease. Additionally, a 20% decrease in passenger service block hours resulted in a decrease in supplemental rent.
Maintenance. Maintenance materials and repair expense increased by $2,732, or 42%, to $9,210 for the three months ended March 31, 2021, as compared to $6,478 for the three months ended March 31, 2020. Our cargo segment was responsible for $2,607 of the consolidated maintenance expense for the three months ended March 31, 2021, as compared to none for the prior year quarter since cargo segment shipments did not begin until May 2020. The cargo segment expense primarily relates to line maintenance, since heavy maintenance is reimbursed under the ATSA.
Sales and Marketing. Sales and marketing expense decreased by $3,462, or 40%, to $5,110 for the three months ended March 31, 2021, as compared to $8,572 for the three months ended March 31, 2020. The passenger revenue decrease between these two periods was 40%, and was primarily due to a $1,980 reduction in credit card processing fees, related to lower sales on our scheduled service. The remaining $1,482 reduction relates to lower advertising costs, global distribution system fees and travel agent commissions, all due to the COVID-19 pandemic.
Depreciation and Amortization. Depreciation and amortization expense increased by $2,088, or 20%, to $12,615 for the three months ended March 31, 2021, as compared to $10,527 for the three months ended