SCHEDULE II—VALUATION AND QUALIFYING ACCOUNTS (in millions) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Balance at beginning of period | | Additions Charged to Costs and Expenses | | Deductions | | Balance at end of period | Year Ended December 31, 2023 | | | | | | | | | Valuation allowance for deferred tax assets | | $ | 90 | | | $ | 69 | | | $ | 6 | | | $ | 153 | | Allowance for obsolete inventory parts | | 29 | | | 6 | | | — | | | 35 | | Allowance for doubtful accounts | | 4 | | | 19 | | | 20 | | (1) | 3 | | Total | | $ | 123 | | | $ | 94 | | | $ | 26 | | | $ | 191 | | Year Ended December 31, 2022 | | | | | | | | | Valuation allowance for deferred tax assets | | $ | 73 | | | $ | 30 | | | $ | 13 | | | $ | 90 | | Allowance for obsolete inventory parts | | 24 | | | 5 | | | — | | | 29 | | Allowance for doubtful accounts | | 3 | | | 16 | | | 15 | | (1) | 4 | | Total | | $ | 100 | | | $ | 51 | | | $ | 28 | | | $ | 123 | | Year Ended December 31, 2021 | | | | | | | | | Valuation allowance for deferred tax assets | | $ | 69 | | | $ | 19 | | | $ | 15 | | | $ | 73 | | Allowance for obsolete inventory parts | | 27 | | | 4 | | | 7 | | | 24 | | Allowance for doubtful accounts | | 2 | | | 14 | | | 13 | | (1) | 3 | | Total | | $ | 98 | | | $ | 37 | | | $ | 35 | | | $ | 100 | |
(1)Uncollectible accounts written off, net of recoveries.
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