NOTES TO CONSOLIDATED FINANCIAL STATEMENTS OF AMERICAN AIRLINES GROUP INC. 5. Debt The table below shows the maximum availability under revolving credit facilities, all of which were undrawn, as of December 31, 2018 (in millions): Secured financings are collateralized by assets, primarily aircraft, engines, simulators, aircraft spare parts, airport gate leasehold rights, route authorities, airport slots and pre-delivery payments. At December 31, 2018, the maturities of long-term debt are as follows (in millions): 99 Long-term debt included in the consolidated balance sheets consisted of (in millions): December 31, 2018 2017 Secured 2013 Credit Facilities, variable interest rate of 4.26%, installments through 2025  (a) $ 1,825 $ 1,825 2014 Credit Facilities, variable interest rate of 4.39%, installments through 2021  (a) 1,215 728 April 2016 Credit Facilities, variable interest rate of 4.52%, installments through 2023  (a) 980 990 December 2016 Credit Facilities, variable interest rate of 4.46%, installments through 2023  (a) 1,225 1,238 Aircraft enhanced equipment trust certificates (EETCs), fixed interest rates ranging from 3.00% to 9.01%, averaging 4.21%, maturing from 2019 to 2029  (b) 11,648 11,881 Equipment loans and other notes payable, fixed and variable interest rates ranging from 2.34% to 8.48%, averaging 4.26%, maturing from 2019 to 2030  (c) 5,060 5,259 Special facility revenue bonds, fixed interest rates ranging from 5.00% to 8.00%, maturing from 2019 to 2031 798 857 Other secured obligations — 2 22,751 22,780 Unsecured 5.50% senior notes, interest only payments until due in 2019  (d) 750 750 4.625% senior notes, interest only payments until due in 2020  (d) 500 500 6.125% senior notes — 500 1,250 1,750 Total long-term debt 24,001 24,530 Less: Total unamortized debt discount, premium and issuance costs 222 236 Less: Current maturities 3,213 2,476 Long-term debt, net of current maturities $ 20,566 $ 21,818 2013 Revolving Facility $ 1,000 2014 Revolving Facility 1,543 April 2016 Revolving Facility 300 Total $ 2,843 2019 $ 3,258 2020 2,320 2021 3,411 2022 1,346 2023 3,894 2024 and thereafter 9,772 Total $ 24,001