CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 271,831	$ 215,723
Marketable securities	640,673	610,185
Receivables, net	56,320	34,462
Inventories, net	98,763	91,196
Other current assets	29,080	31,236
Total current assets	1,096,667	982,802
PROPERTY AND EQUIPMENT:
Aircraft and rotable spares	7,529,226	7,527,555
Deposits on aircraft	121,293	31,625
Buildings and ground equipment	256,348	258,863
Total property and equipment, gross	7,906,867	7,818,043
Less-accumulated depreciation and amortization	(2,621,410)	(2,455,995)
Total property and equipment, net	5,285,457	5,362,048
OTHER ASSETS:
Operating lease right-of-use assets	248,576	282,362
Long-term receivables and other assets	309,802	260,410
Total other assets	558,378	542,772
Total assets	6,940,502	6,887,622
CURRENT LIABILITIES:
Current maturities of long-term debt	359,888	402,158
Accounts payable	427,903	278,677
Accrued salaries, wages and benefits	146,947	125,944
Current maturities of operating lease liabilities	78,188	82,641
Taxes other than income taxes	30,333	26,183
Other current liabilities	94,496	26,119
Total current liabilities	1,137,755	941,722
LONG-TERM DEBT, net of current maturities	2,605,063	2,801,538
DEFERRED INCOME TAXES PAYABLE	657,067	625,931
NONCURRENT OPERATING LEASE LIABILITIES	171,443	205,845
OTHER LONG-TERM LIABILITIES	107,367	173,041
COMMITMENTS AND CONTINGENCIES (Note 7)
STOCKHOLDERS' EQUITY:
Preferred stock, 5,000,000 shares authorized; none issued
Common stock, no par value, 120,000,000 shares authorized; 82,335,782 and 82,094,985 shares issued as of September 30, 2021, and December 31, 2020, respectively	720,932	704,675
Retained earnings	2,159,584	2,052,006
Treasury stock, at cost, 31,955,991 and 31,913,635 shares as of September 30, 2021, and December 31, 2020, respectively	(618,709)	(617,136)
Total stockholders' equity	2,261,807	2,139,545
Total liabilities and stockholders' equity	$ 6,940,502	$ 6,887,622