NOTES TO CONSOLIDATED FINANCIAL STATEMENTS OF AMERICAN AIRLINES, INC. The estimated amount of unrecognized actuarial net loss and prior service cost for the defined benefit pension plans that will be amortized from AOCI into net periodic benefit cost over the next fiscal year is $181 million. The estimated amount of unrecognized actuarial net gain and prior service benefit for the retiree medical and other postretirement benefits plans that will be amortized from AOCI into net periodic benefit cost over the next fiscal year is $269 million. The following actuarial assumptions were used to determine American’s benefit obligations and net periodic benefit cost for the periods presented: As of December 31, 2018, American’s estimate of the long-term rate of return on plan assets was 8% based on the target asset allocation. Expected returns on long duration bonds are based on yields to maturity of the bonds held at year-end. Expected returns on other assets are based on a combination of long-term historical returns, actual returns on plan assets achieved over the last ten years, current and expected market conditions, and expected value to be generated through active management and securities lending programs. A one percentage point change in the assumed health care cost trend rates would have the following effects on American’s retiree medical and other postretirement benefits plans (in millions): $^{(1)}$  The weighted average health care cost trend rate at December 31, 2018 is assumed to decline gradually to 3.45% by 2026 and remain level thereafter. American is required to make minimum contributions to its defined benefit pension plans under the minimum funding requirements of the Employee Retirement Income Security Act of 1974 (ERISA) and various other laws for U.S. based plans as well as underfunding rules specific to countries where American maintains defined benefit plans. Based on current funding assumptions, American has minimum required contributions of $780 million for 2019. American expects to make supplemental contributions of $21 million to its U.S. based defined benefit pension plans in 2019. American’s funding obligations will depend on the performance of American’s investments held in trust by the pension plans, interest rates for determining liabilities, the amount of and timing of any supplemental contributions and American’s actuarial experience. 160 Minimum Contributions 1% Increase 1% Decrease Increase (decrease) on 2018 service and interest cost $ 2 $ (2 ) Increase (decrease) on benefit obligation as of December 31, 2018 47 (43) Assumptions Pension Benefits Retiree Medical and Other Postretirement Benefits 2018 2017 2016 2018 2017 2016 Net periodic benefit cost: Weighted average discount rate 3.80% 4.30% 4.70% 3.60% 4.10% 4.42% Weighted average expected rate of return on plan assets 8.00% 8.00% 8.00% 8.00% 8.00% 8.00% Weighted average health care cost trend rate assumed for next year  (1) N/A N/A N/A 3.91% 4.19% 4.25% Pension Benefits Retiree Medical and Other Postretirement Benefits 2018 2017 2018 2017 Benefit obligations: Weighted average discount rate 4.40% 3.80% 4.30% 3.60%