Leases - Related Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Assets
Accumulated amortization	$ 634	$ 679
Operating	1,394	1,590
Finance	297	556
Total lease assets	$ 1,691	$ 2,146
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Flight equipment	Flight equipment
Current
Operating	$ 225	$ 239
Finance	$ 42	$ 82
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt and Lease Obligation, Current	Long-Term Debt and Lease Obligation, Current
Noncurrent
Operating	$ 1,118	$ 1,315
Finance	$ 147	$ 377
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt less current maturities	Long-term debt less current maturities
Total lease liabilities	$ 1,532	$ 2,013