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Fair Value Measurements - Measured on Recurring Basis (Details) - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Fuel derivatives: |  |
Option contracts | $ 280 | $ 223
Fair Value, Measurements, Recurring |  |
Assets |  |
Treasury bills | 1,934 | 1,983
Fuel derivatives: |  |
Equity Securities | 286 | 280
Total assets | 11,078 | 11,977
Fair Value, Measurements, Recurring | Option contracts |  |
Fuel derivatives: |  |
Option contracts | 280 | 223
Fair Value, Measurements, Recurring | Option contracts |  |
Liabilities |  |
Option contracts | (23) |
Fair Value, Measurements, Recurring | Certificates of deposit |  |
Assets |  |
Certificates of deposit | 211 | 203
Fair Value, Measurements, Recurring | Cash equivalents |  |
Assets |  |
Cash equivalents | 8,119 | 9,032
Fair Value, Measurements, Recurring | Commercial paper |  |
Assets |  |
Cash equivalents | 135 | 135
Fair Value, Measurements, Recurring | Certificates of deposit |  |
Assets |  |
Cash equivalents | 13 | 21
Fair Value, Measurements, Recurring | Time deposits |  |
Assets |  |
Cash equivalents | 100 | 100
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) |  |
Assets |  |
Treasury bills | 1,934 | 1,983
Fuel derivatives: |  |
Equity Securities | 286 | 280
Total assets | 10,339 | 11,295
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Option contracts |  |
Fuel derivatives: |  |
Option contracts | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Option contracts |  |
Liabilities |  |
Option contracts | 0 |
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Certificates of deposit |  |
Assets |  |
Certificates of deposit | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Cash equivalents |  |
Assets |  |
Cash equivalents | 8,119 | 9,032
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Commercial paper |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Certificates of deposit |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1) | Time deposits |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) |  |
Assets |  |
Treasury bills | 0 | 0
Fuel derivatives: |  |
Equity Securities | 0 | 0
Total assets | 459 | 459
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Option contracts |  |
Fuel derivatives: |  |
Option contracts | 0 | 0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Option contracts |  |
Liabilities |  |
Option contracts | 0 |
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Certificates of deposit |  |
Assets |  |
Certificates of deposit | 211 | 203
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Cash equivalents |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Commercial paper |  |
Assets |  |
Cash equivalents | 135 | 135
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Certificates of deposit |  |
Assets |  |
Cash equivalents | 13 | 21
Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2) | Time deposits |  |
Assets |  |
Cash equivalents | 100 | 100
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) |  |
Assets |  |
Treasury bills | 0 | 0
Fuel derivatives: |  |
Equity Securities | 0 | 0
Total assets | 280 | 223
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Option contracts |  |
Fuel derivatives: |  |
Option contracts | 280 | 223
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Option contracts |  |
Liabilities |  |
Option contracts | (23) |
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Certificates of deposit |  |
Assets |  |
Certificates of deposit | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Cash equivalents |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Commercial paper |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Certificates of deposit |  |
Assets |  |
Cash equivalents | 0 | 0
Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3) | Time deposits |  |
Assets |  |
Cash equivalents | $ 0 | $ 0

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