NOTES TO CONSOLIDATED FINANCIAL STATEMENTS OF AMERICAN AIRLINES, INC. $^{(10)}$  Impact of the 2017 Tax Act includes a $924 million non-cash charge to income tax expense to reflect the impact of lower corporate income tax rates on the Company’s deferred tax asset and liabilities resulting from the 2017 Tax Act, which reduced the federal corporate income tax rate from 35% to 21%. 3. Debt Long-term debt included on American’s consolidated balance sheets consisted of (in millions): December 31, 2019 2018 Secured 2013 Credit Facilities, variable interest rate of 3.54%, installments through 2025  (a) $ 1,807 $ 1,825 2014 Credit Facilities, variable interest rate of 3.72%, installments through 2021  (a) 1,202 1,215 April 2016 Credit Facilities, variable interest rate of 3.80%, installments through 2023  (a) 970 980 December 2016 Credit Facilities, variable interest rate of 3.74%, installments through 2023  (a) 1,213 1,225 Enhanced equipment trust certificates (EETCs), fixed interest rates ranging from 3.00% to 8.39%, averaging 4.05%, maturing from 2020 to 2032  (b) 11,933 11,648 Equipment loans and other notes payable, fixed and variable interest rates ranging from 2.99% to 7.31%, averaging 3.45%, maturing from 2020 to 2031  (c) 4,727 5,060 Special facility revenue bonds, fixed interest rates of 5.00%, maturing from 2020 to 2031 725 769 Total long-term debt 22,577 22,722 Less: Total unamortized debt discount, premium and issuance costs 205 219 Less: Current maturities 2,246 2,466 Long-term debt, net of current maturities $ 20,126 $ 20,037 2013 Revolving Facility $ 750 2014 Revolving Facility 1,643 April 2016 Revolving Facility 450 Other Short-term Revolving Facility 400 Total $ 3,243 The table below shows the maximum availability under revolving credit facilities, all of which were undrawn, as of December 31, 2019 (in millions): Secured financings are collateralized by assets, primarily aircraft, engines, simulators, aircraft spare parts, airport gate leasehold rights, route authorities, airport slots and certain pre-delivery payments. At December 31, 2019, the maturities of long-term debt are as follows (in millions): 2020 $ 2,293 2021 3,508 2022 1,551 2023 4,072 2024 1,521 2025 and thereafter 9,632 Total $ 22,577 131