Aircraft rentals. The $20.3 million, or 79.4%, decrease in aircraft rentals was primarily related to early lease buyouts we executed during 2023. During 2023, we acquired 26 CRJ700 aircraft, eight CRJ200 aircraft and one CRJ900 aircraft under early lease buyouts.
Other operating expenses. Other operating expenses primarily consist of property taxes, hull and liability insurance, simulator costs, crew per diem, crew hotel costs and credit loss reserves. The $26.2 million, or 9.8%, increase in other operating expenses was primarily related to an increase in other operating costs, such as crew per diem and crew hotel costs, as a result of the higher number of flights we operated during 2024, compared to 2023.
Summary of interest expense, interest income, other income (expense) and provision for income taxes:
Interest Expense. The $16.6 million, or 12.7%, decrease in interest expense was primarily related to a decrease in outstanding debt from $3.0 billion at December 31, 2023 to $2.7 billion at December 31, 2024. Our average effective interest rate for 2024 and 2023 was 4.2% and 4.1%, respectively.
Interest income. Interest income increased $4.0 million, from $43.9 million during the year ended December 31, 2023 to $47.9 million during the year ended December 31, 2024. Our interest income increased primarily from an increase in average interest rates attributed to our marketable securities for the year ended December 31, 2024, compared to the year ended December 31, 2023.
Other income, net. Other income, net decreased $19.4 million in 2024, compared to 2023. Other income, net primarily consists of the realized and unrealized gains or losses on our investments in other companies, income or loss related to our equity method investments and gains or losses on the sale of assets. The decrease in other income, net was primarily due to a decrease in gains from the sale of assets and a decrease in unrealized gains on our investments in other companies for the year ended December 31, 2024, compared to the year ended December 31, 2023.
Provision for income taxes. For the years ended December 31, 2024, and December 31, 2023, our effective income tax rates were 25.3% and 14.8%, respectively, which included the statutory federal income tax rate of 21% and other reconciling income tax items, including state income taxes and the impact of non-deductible expenses. For the year ended December 31, 2023, the lower effective tax rate was primarily related to a benefit of $7.6 million for the release of a previously recorded uncertain tax position liability. Our income tax provision rate may fluctuate each reporting period based on various factors including, but not limited to, the amount of our non-deductible operating expenses, relative to our income before income taxes.
Net Income. Primarily due to the factors described above, we generated net income of $323.0 million, or $7.77 per diluted share, for the year ended December 31, 2024, compared to net income of $34.3 million, or $0.77 per diluted share, for the year ended December 31, 2023.
Our Business Segments 2024 compared to 2023:
Our reporting segments consist of (1) the operations of SkyWest Airlines and SWC, which had its first revenue generating flight in 2023, (collectively, “SkyWest Airlines and SWC”) and (2) SkyWest Leasing activities.
Our chief operating decision maker analyzes the profitability of operating aircraft under our code-share agreements separately from the profitability of financing new aircraft acquired through debt and cash placed under our capacity purchase agreements, currently consisting of our E175 fleet, and our return on such aircraft financing. The SkyWest Airlines and SWC segment includes revenue earned under the applicable capacity purchase agreements attributed to operating such aircraft and the respective operating costs, and revenue and operating expenses attributed to other flying or airport services agreements and charter flight services. The SkyWest Leasing segment includes applicable revenue earned under the applicable capacity purchase agreements attributed to the ownership of new aircraft acquired through the issuance of debt and the respective depreciation and interest expense of such aircraft. The SkyWest Leasing segment also includes the activity of acquiring and leasing used regional jet aircraft and spare engines to third parties and other activities. The SkyWest Leasing segment’s total assets and capital expenditures include new aircraft acquired through the issuance of debt and our aircraft and engines leased to third parties. Additionally, aircraft removed from SkyWest Airlines operations and held for sale are included in the SkyWest Leasing segment.