CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current Assets
Cash and cash equivalents	$ 495	$ 1,370
Marketable securities	2,700	1,976
Total cash and marketable securities	3,195	3,346
Receivables - net	536	480
Inventories and supplies - net	62	57
Prepaid expenses, assets held-for-sale, and other current assets	208	123
Total Current Assets	4,001	4,006
Property and Equipment
Aircraft and other flight equipment	8,076	7,761
Other property and equipment	1,446	1,398
Deposits for future flight equipment	378	583
Property and Equipment Total	9,900	9,742
Less accumulated depreciation and amortization	3,780	3,531
Total Property and Equipment - Net	6,120	6,211
Operating Lease, Right-of-Use Asset	1,370	1,400
Goodwill	1,943	1,943
Intangible assets - net	102	107
Other noncurrent assets	346	379
Other Assets	3,761	3,829
Total Assets	13,882	14,046
Current Liabilities
Accounts payable	181	108
Accrued wages, vacation and payroll taxes	426	527
Other accrued liabilities	603	424
Operating Lease, Liability, Current	260	290
Current portion of long-term debt	425	1,138
Total Current Liabilities	4,024	4,293
Long-Term Debt, Net of Current Portion	2,225	2,357
Noncurrent Liabilities
Operating Lease, Liability, Noncurrent	1,206	1,268
Deferred Income Tax Liabilities, Net	501	407
Deferred revenue, noncurrent	1,446	1,544
Obligation for pension and postretirement medical benefits	558	665
Other liabilities	391	524
Other Liabilities and Credits Totals	4,102	4,408
Commitments and Contingencies
Shareholders' Equity
Preferred stock, $0.01 par value, Authorized: 5,000,000 shares, none issued or outstanding	0	0
Common stock, $0.01 par value, Authorized: 400,000,000 shares, Issued: 2021 - 133,792,045 shares; 2020 - 133,567,534 shares, Outstanding: 2021 - 124,442,101 shares; 2020 - 124,217,590 shares	1	1
Capital in excess of par value	462	391
Treasury stock (common), at cost: 2020 - 9,349,944 shares; 2020 - 9,349,944 shares	(674)	(674)
Accumulated other comprehensive loss	(482)	(494)
Retained earnings	4,224	3,764
Total Shareholders' Equity	$ 3,531	2,988
Preferred Stock, par value (usd per share)	$ 0.01
Total Liabilities and Shareholders' Equity	$ 13,882	14,046
Mileage Plan Revenue [Member]
Current Liabilities
Contract with Customer, Liability, Current	904	733
Contract with Customer, Liability, Current	904	733
Passenger Revenue [Member]
Current Liabilities
Contract with Customer, Liability, Current	1,225	1,073
Contract with Customer, Liability, Current	$ 1,225	$ 1,073