Condensed Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 1,122,139	$ 1,004,733
Short-term investment securities	103,491	102,789
Accounts receivable, net	70,946	47,660
Aircraft maintenance deposits, net	129,838	106,901
Prepaid expenses and other current assets	90,346	83,383
Total current assets	1,516,760	1,345,466
Property and equipment:
Flight equipment	3,322,618	3,257,215
Ground property and equipment	201,579	191,661
Less accumulated depreciation	(369,405)	(332,864)
Total property and equipment	3,154,792	3,116,012
Operating lease right-of-use assets	1,046,262	0
Pre-delivery deposits on flight equipment	264,419	236,775
Long-term aircraft maintenance deposits	118,359	138,738
Deferred heavy maintenance, net	280,118	249,010
Other long-term assets	43,229	79,456
Total assets	6,423,939	5,165,457
Current liabilities:
Accounts payable	26,713	39,320
Air traffic liability	403,001	291,981
Current maturities of long-term debt and finance leases	173,413	163,557
Current maturities of operating leases	128,138	0
Other current liabilities	395,404	339,677
Total current liabilities	1,126,669	834,535
Long-term debt and finance leases, less current maturities	2,039,619	2,024,774
Operating leases, less current maturities	895,056	0
Deferred income taxes	366,854	355,141
Deferred gains and other long-term liabilities	18,085	22,503
Shareholders’ equity:
Common stock	7	7
Additional paid-in-capital	374,896	371,225
Treasury stock, at cost	(72,239)	(67,016)
Retained earnings	1,676,008	1,625,481
Accumulated other comprehensive income (loss)	(1,016)	(1,193)
Total shareholders’ equity	1,977,656	1,928,504
Total liabilities and shareholders’ equity	$ 6,423,939	$ 5,165,457