CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 215,723	$ 87,206
Marketable securities	610,185	432,966
Income tax receivable	3,916	11,141
Receivables, net	34,462	82,977
Inventories, net	91,196	110,503
Other current assets	27,320	35,553
Total current assets	982,802	760,346
PROPERTY AND EQUIPMENT:
Aircraft and rotable spares	7,527,555	7,078,801
Deposits on aircraft	31,625	48,858
Buildings and ground equipment	258,863	265,398
Total property and equipment, gross	7,818,043	7,393,057
Less-accumulated depreciation and amortization	(2,455,995)	(1,998,376)
Total property and equipment, net	5,362,048	5,394,681
OTHER ASSETS
Operating lease right-of-use assets	282,362	336,009
Other long-term assets	260,410	166,093
Total other assets	542,772	502,102
Total assets	6,887,622	6,657,129
CURRENT LIABILITIES:
Current maturities of long-term debt	402,158	364,126
Accounts payable	278,677	284,473
Accrued salaries, wages and benefits	125,944	133,856
Current maturities of operating lease liabilities	82,641	94,806
Taxes other than income taxes	26,183	15,004
Other current liabilities	26,119	32,411
Total current liabilities	941,722	924,676
LONG-TERM DEBT, net of current maturities	2,801,538	2,628,989
DEFERRED INCOME TAXES PAYABLE	625,931	623,580
NONCURRENT OPERATING LEASE LIABILITIES	205,845	259,237
OTHER LONG-TERM LIABILITIES	173,041	45,633
COMMITMENTS AND CONTINGENCIES (Note 6)
STOCKHOLDERS' EQUITY:
Preferred stock, 5,000,000 shares authorized; none issued
Common stock, no par value, 120,000,000 shares authorized; 82,094,985 and 81,742,937 shares issued, respectively	704,675	686,806
Retained earnings	2,052,006	2,079,179
Treasury stock, at cost, 31,913,635 and 31,420,179 shares, respectively	(617,136)	(590,971)
Total stockholders' equity	2,139,545	2,175,014
Total liabilities and stockholders' equity	$ 6,887,622	$ 6,657,129