CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 221	$ 105	$ 194
Marketable securities	1,300	1,131
Total cash and marketable securities	1,521	1,236
Receivables - net	323	366
Inventories and supplies - net	72	60
Prepaid expenses and other current assets	121	125
Total Current Assets	2,037	1,787
Property and Equipment
Aircraft and other flight equipment	8,549	8,221
Other property and equipment	1,306	1,363
Deposits for future flight equipment	533	439
Property and Equipment	10,388	10,023
Less accumulated depreciation and amortization	3,486	3,242
Total Property and Equipment - Net	6,902	6,781
Other Assets
Operating Lease, Right-of-Use Asset	1,711	0
Goodwill	1,943	1,943
Intangible assets - net	122	127
Other noncurrent assets	278	274
Total Other Assets	4,054	2,344
Total Assets	12,993	10,912
Current Liabilities
Accounts payable	146	132
Accrued wages, vacation and payroll taxes	470	415
Air traffic liability	900	788
Other accrued liabilities	431	416
Deferred revenue	750	705
Operating Lease, Liability, Current	269	0
Current portion of long-term debt	235	486
Total Current Liabilities	3,201	2,942
Long-Term Debt, Net of Current Portion	1,264	1,617
Other Liabilities and Credits
Operating Lease, Liability, Noncurrent	1,439	0
Deferred income taxes	715	512
Deferred revenue	1,240	1,169
Obligation for pension and postretirement medical benefits	571	503
Other liabilities	232	418
Total Other Liabilities and Credits	4,197	2,602
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: 2019 - 131,812,173 shares; 2018 - 130,813,476 shares, Outstanding: 2019 - 123,000,307 shares; 2018 - 123,194,430 shares	1	1
Capital in excess of par value	305	232
Treasury stock (common), at cost: 2019 - 8,811,866 shares; 2018 - 7,619,046 shares	(643)	(568)
Accumulated other comprehensive loss	(465)	(448)
Retained earnings	5,133	4,534
Shareholders' Equity Total	4,331	3,751	$ 3,460	$ 2,744
Total Liabilities and Shareholders' Equity	$ 12,993	$ 10,912