Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net earnings (loss)	$ 7,532		$ (26,680)	$ 26,924
Adjustments to reconcile net earnings to net cash (used in) provided by operating activities:
Depreciation and amortization	68,027		65,743	71,618
Deferred income taxes	(59,272)		(2,424)	12,894
Gain (loss) on asset dispositions	298		(3,350)	339
Equity in loss (income) of unconsolidated affiliate	385		(151)	306
Impairment of assets	368		407	0
Inventory valuation reserves	2,410		5,179	3,231
Other	0		0	(1,277)
Changes in operating assets and liabilities:
Accounts receivable	(28,329)	[1]	(351)	36,579
Inventories of spare parts	(6,793)	[1]	(5,064)	1,441
Income taxes receivable	186	[1]	220	466
Other assets	(9,050)	[1]	(14,837)	(14,998)
Accounts payable and accrued liabilities	5,754	[1]	(19,111)	(3,859)
Other long-term liabilities	(619)	[1]	(142)	254
Net cash (used in) provided by operating activities	(19,103)	[1]	(564)	133,918
Investing activities:
Purchase of property and equipment	(56,757)		(81,842)	(57,123)
Proceeds from asset dispositions	1,296		14,983	5,236
Purchase of short-term investments	(637,980)		(321,453)	(608,649)
Proceeds from sale of short-term investments	862,942		316,543	505,966
Payments of deposits on aircraft	0		(2,249)	(1,273)
Refunds of deposits on aircraft	0		0	6,010
Loan to unconsolidated affiliate	0		(1,200)	0
Loan to third party	(824)		0	0
Business acquisitions net of cash acquired	(126,644)		0	0
Net cash provided by (used in) investing activities	42,033		(75,218)	(149,833)
Financing activities:
Repurchase of common stock	(256)		(529)	(2,448)
Proceeds from line of credit	152,150		264,700	232,660
Payments on line of credit	(168,650)		(188,200)	(218,160)
Net cash provided by financing activities	(16,756)		75,971	12,052
Increase (decrease) in cash	6,174		189	(3,863)
Cash, beginning of year	2,596		2,407	6,270
Cash, end of year	8,770		2,596	2,407
Cash paid during the period for:
Interest	30,517		29,169	27,657
Income Taxes	1,231		2,637	5,521
Accrued payables related to purchases of property and equipment	$ 42		$ 29	$ 1,339

[1] Net of the effect of business acquisitions.