CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Current Assets
Cash and cash equivalents	$ 1,076	$ 1,370
Marketable securities	2,473	1,976
Total cash and marketable securities	3,549	3,346
Receivables - net	517	480
Inventories and supplies - net	57	57
Prepaid expenses, assets held-for-sale, and other current assets	161	123
Total Current Assets	4,284	4,006
Property and Equipment
Aircraft and other flight equipment	7,933	7,761
Other property and equipment	1,407	1,398
Deposits for future flight equipment	420	583
Property and Equipment Total	9,760	9,742
Less accumulated depreciation and amortization	3,616	3,531
Total Property and Equipment - Net	6,144	6,211
Operating Lease, Right-of-Use Asset	1,423	1,400
Goodwill	1,943	1,943
Intangible assets - net	105	107
Other noncurrent assets	363	379
Other Assets	3,834	3,829
Total Assets	14,262	14,046
Current Liabilities
Accounts payable	133	108
Accrued wages, vacation and payroll taxes	456	527
Other accrued liabilities	541	424
Operating Lease, Liability, Current	271	290
Current portion of long-term debt	1,246	1,138
Total Current Liabilities	4,762	4,293
Long-Term Debt, Net of Current Portion	2,325	2,357
Noncurrent Liabilities
Operating Lease, Liability, Noncurrent	1,283	1,268
Deferred Income Tax Liabilities, Net	365	407
Deferred revenue, noncurrent	1,507	1,544
Obligation for pension and postretirement medical benefits	663	665
Other liabilities	482	524
Other Liabilities and Credits Totals	4,300	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	409	391
Treasury stock (common), at cost: 2020 - 9,349,944 shares; 2020 - 9,349,944 shares	(674)	(674)
Accumulated other comprehensive loss	(494)	(494)
Retained earnings	3,633	3,764
Total Shareholders' Equity	$ 2,875	2,988
Preferred Stock, par value (usd per share)	$ 0.01
Total Liabilities and Shareholders' Equity	$ 14,262	14,046
Mileage Plan Revenue [Member]
Current Liabilities
Contract with Customer, Liability, Current	818	733
Contract with Customer, Liability, Current	818	733
Passenger Revenue [Member]
Current Liabilities
Contract with Customer, Liability, Current	1,297	1,073
Contract with Customer, Liability, Current	$ 1,297	$ 1,073