SkyWest (SKYW) 10-K 22 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 16, 2021	Jun. 30, 2020
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	0-14719
Entity Registrant Name	SKYWEST INC
Entity Incorporation, State or Country Code	UT
Entity Tax Identification Number	87-0292166
Entity Address, Address Line One	444 South River Road
Entity Address, City or Town	St. George
Entity Address, State or Province	UT
Entity Address, Postal Zip Code	84790
City Area Code	435
Local Phone Number	634-3000
Title of 12(b) Security	Common Stock, No Par Value
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,635,572,360
Trading Symbol	SKYW
Entity Common Stock, Shares Outstanding		50,344,080
Entity Central Index Key	0000793733
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

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

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED BALANCE SHEETS
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	82,094,985	81,742,937
Treasury stock, at cost, shares	31,913,635	31,420,179

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING REVENUES:
Total operating revenues	$ 2,127,106	$ 2,971,963	$ 3,221,679
OPERATING EXPENSES:
Salaries, wages and benefits	826,109	1,001,746	1,201,518
Depreciation and amortization	474,959	368,098	334,589
CARES Act payroll support grant	(345,491)
Special items		21,869
Other operating expenses	222,797	243,729	272,826
Total operating expenses	2,018,304	2,459,705	2,747,399
OPERATING INCOME	108,802	512,258	474,280
OTHER INCOME (EXPENSE):
Interest income	5,879	14,131	8,823
Interest expense	(123,173)	(127,755)	(120,409)
Other, net	1,165	47,671	3,620
Total other expense, net	(116,129)	(65,953)	(107,966)
INCOME (LOSS) BEFORE INCOME TAXES	(7,327)	446,305	366,314
PROVISION FOR INCOME TAXES	1,188	106,206	85,942
NET INCOME (LOSS)	$ (8,515)	$ 340,099	$ 280,372
BASIC EARNINGS (LOSS) PER SHARE (in dollars per share)	$ (0.17)	$ 6.68	$ 5.40
DILUTED EARNINGS (LOSS) PER SHARE (in dollars per share)	$ (0.17)	$ 6.62	$ 5.30
Weighted average common shares:
Basic (in shares)	50,195,000	50,932,000	51,914,000
Diluted (in shares)	50,195,000	51,375,000	52,871,000
COMPREHENSIVE INCOME (LOSS):
Net income (loss)	$ (8,515)	$ 340,099	$ 280,372
Net unrealized appreciation on marketable securities, net of taxes		32	18
TOTAL COMPREHENSIVE INCOME (LOSS)	(8,515)	340,131	280,390
Flying agreements
OPERATING REVENUES:
Total operating revenues	2,060,801	2,889,265	3,169,520
Lease, airport services and other
OPERATING REVENUES:
Total operating revenues	66,305	82,698	52,159
Aircraft maintenance, materials and repairs
OPERATING EXPENSES:
Total operating expenses	618,989	514,313	556,259
Aircraft fuel
OPERATING EXPENSES:
Total operating expenses	61,739	119,115	117,657
Airport related expenses
OPERATING EXPENSES:
Total operating expenses	93,886	118,837	109,605
Aircraft rentals
OPERATING EXPENSES:
Total operating expenses	$ 65,316	$ 71,998	$ 154,945

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common StockCumulative Effect, Period of Adoption, as Adjusted	Common Stock	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Retained EarningsCumulative Effect, Period of Adoption, as Adjusted	Retained Earnings	Treasury StockCumulative Effect, Period of Adoption, as Adjusted	Treasury Stock	Accumulated Other Comprehensive Income (Loss)Cumulative Effect, Period of Adoption, as Adjusted	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, as Adjusted	Total
Balance at Dec. 31, 2017		$ 672,593			$ 1,516,957		$ (435,178)		$ (50)			$ 1,754,322
Balance (in shares) at Dec. 31, 2017		80,398					(28,644)
Increase (Decrease) in Stockholders' Equity
Net income (loss)					280,372							280,372
Net unrealized appreciation on marketable securities, net of tax									18			18
Exercise of common stock options and vested restricted stock units		$ 2,174										2,174
Exercise of common stock options and vested restricted stock units (in shares)		780
Shares acquired from vested employee stock awards for income tax withholdings							$ (13,556)					(13,556)
Shares acquired from vested employee stock awards for income tax withholdings (in shares)							(239)
Sale of common stock under employee stock purchase plan		$ 3,038										3,038
Sale of common stock under employee stock purchase plan (in shares)		61
Stock based compensation expense		$ 13,105										13,105
Treasury stock purchases							$ (54,448)					(54,448)
Treasury stock purchases (in shares)							(968)
Cash dividends declared					(20,744)							(20,744)
Balance at Dec. 31, 2018	$ 690,910	$ 690,910	$ (13,141)	$ 1,763,444	1,776,585	$ (503,182)	$ (503,182)	$ (32)	(32)	$ (13,141)	$ 1,951,140	1,964,281
Balance (in shares) at Dec. 31, 2018	81,239	81,239				(29,851)	(29,851)
Increase (Decrease) in Stockholders' Equity
Net income (loss)					340,099							340,099
Net unrealized appreciation on marketable securities, net of tax									$ 32			32
Exercise of common stock options and vested restricted stock units		$ 3,106										3,106
Exercise of common stock options and vested restricted stock units (in shares)		707
Shares acquired from vested employee stock awards for income tax withholdings							$ (9,313)					(9,313)
Shares acquired from vested employee stock awards for income tax withholdings (in shares)							(173)
Sale of common stock under employee stock purchase plan		$ 3,165										3,165
Sale of common stock under employee stock purchase plan (in shares)		65
Stock based compensation expense		$ 5,770										5,770
Common stock purchased and cancelled		$ (16,145)										(16,145)
Common stock purchased and cancelled (in shares)		(268)
Treasury stock purchases							$ (78,476)					(78,476)
Treasury stock purchases (in shares)							(1,396)
Cash dividends declared					(24,364)							(24,364)
Balance at Dec. 31, 2019	$ 686,806	$ 686,806	$ (11,639)	$ 2,067,540	2,079,179	$ (590,971)	$ (590,971)			$ (11,639)	$ 2,163,375	2,175,014
Balance (in shares) at Dec. 31, 2019	81,743	81,743				(31,420)	(31,420)
Increase (Decrease) in Stockholders' Equity
Net income (loss)					(8,515)							(8,515)
Exercise of common stock options and vested restricted stock units		$ 38										38
Exercise of common stock options and vested restricted stock units (in shares)		287
Shares acquired from vested employee stock awards for income tax withholdings							$ (6,165)					(6,165)
Shares acquired from vested employee stock awards for income tax withholdings (in shares)							(108)
Sale of common stock under employee stock purchase plan		$ 2,781										2,781
Sale of common stock under employee stock purchase plan (in shares)		65
Stock based compensation expense		$ 6,802										6,802
Treasury stock purchases							$ (20,000)					(20,000)
Treasury stock purchases (in shares)							(386)
Cash dividends declared					(7,019)							(7,019)
Warrants issued under CARES Act agreements		8,248										8,248
Balance at Dec. 31, 2020		$ 704,675			$ 2,052,006		$ (617,136)					$ 2,139,545
Balance (in shares) at Dec. 31, 2020		82,095					(31,914)

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
Net unrealized appreciation (depreciation) on marketable securities, tax		$ 10	$ 6
Cash dividends declared (in dollars per share)	$ 0.14	$ 0.48	$ 0.40

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (8,515)	$ 340,099	$ 280,372
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	474,959	368,098	334,589
Stock based compensation expense	6,802	10,274	13,105
Write-off of maintenance assets	3,255
Increase in credit loss reserves	17,087
Loss on disposal of fixed assets	445
Net increase in deferred income taxes	6,100	109,654	99,139
Gain on sale of ExpressJet subsidiary		(46,525)
Special items		21,869
Changes in operating assets and liabilities:
Decrease (increase) in receivables	26,831	(40,700)	(21,464)
Decrease (increase) in income tax receivable	7,225	14,795	(20,620)
Decrease (increase) in inventories	19,307	(4,303)	(7,935)
Decrease in other current assets	8,233	2,707	77,484
Decrease in operating lease right-of-use assets	53,647
Increase in operating lease liabilities	(65,557)	(895)
Increase in deferred revenue	110,728
Decrease in deferred aircraft credits			(14,243)
Increase (decrease) in accounts payable and other current liabilities	(26,984)	(54,043)	62,107
NET CASH PROVIDED BY OPERATING ACTIVITIES	633,563	721,030	802,534
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(1,347,775)	(1,938,750)	(2,308,768)
Sales of marketable securities	1,170,556	1,866,761	2,451,344
Net cash received from sale of ExpressJet subsidiary		53,200
Acquisition of property and equipment:
Aircraft and rotable spare parts	(425,618)	(581,329)	(1,062,380)
Buildings and ground equipment	(12,678)	(80,586)	(34,397)
Proceeds from the sale of aircraft, property and equipment	3,239	26,008
Deposits on aircraft	(9,625)	(52,817)	(41,937)
Return of deposits applied towards acquired aircraft	27,858	46,346	49,550
Decrease (increase) in other assets	(89,428)	4,133	(36,816)
NET CASH USED IN INVESTING ACTIVITIES	(683,471)	(657,034)	(983,404)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	406,364	200,040	784,665
Principal payments on long-term debt	(187,404)	(382,442)	(370,775)
Net proceeds from issuance of common stock	2,819	6,271	5,212
Purchase of treasury stock	(20,000)	(78,476)	(54,448)
Purchase of common stock		(16,145)
Employee income tax paid on vested equity awards	(6,165)	(9,313)	(13,556)
Payment of debt issuance cost	(4,130)	(1,642)	(3,892)
Payment of cash dividends	(13,059)	(23,467)	(19,744)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	178,425	(305,174)	327,462
Increase (decrease) in cash and cash equivalents	128,517	(241,178)	146,592
Cash and cash equivalents at beginning of period	87,206	328,384	181,792
CASH AND CASH EQUIVALENTS AT END OF PERIOD	215,723	87,206	328,384
Non-cash investing and financing activities:
Acquisition of rotable spare parts	22,187	16,514	367
Debt assumed on aircraft acquired under operating leases		14,475	59,132
Engines contributed to joint venture		22,313
Non-cash assets used to acquire aircraft under operating leases		153,566
Lease liability arising from the recognition of right-of-use asset		456,472
Warrants issued under CARES Act agreements	8,248
Cash paid during the period for:
Interest, net of capitalized amounts	125,440	131,733	118,268
Income taxes	$ 1,780	2,490	$ 2,661
SUPPLEMENTAL DISCLOSURE OF SALE OF SUBSIDIARY:
Decrease in carrying amount of assets		(101,448)
Decrease in carrying amount of liabilities		68,341
Cash received from buyers		79,632
Gain on sale of subsidiary		$ 46,525

Nature of Operations and Summar

Nature of Operations and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Nature of Operations and Summary of Significant Accounting Policies
Nature of Operations and Summary of Significant Accounting Policies	(1) Nature of Operations and Summary of Significant Accounting Policies SkyWest, Inc. (the “Company”), through its subsidiary, SkyWest Airlines, Inc. (“SkyWest Airlines”) operates the largest regional airline in the United States. On January 22, 2019, the Company completed the sale of its former wholly owned subsidiary, ExpressJet Airlines, Inc. (“ExpressJet”). As of December 31, 2020, SkyWest Airlines offered scheduled passenger service under code-share agreements with Delta Air Lines, Inc. (“Delta”), United Airlines, Inc. (“United”), American Airlines, Inc. (“American”) and Alaska Airlines, Inc. (“Alaska”) with approximately 1,770 total daily departures to destinations in the United States, Canada, Mexico and the Caribbean. Additionally, the Company provides airport customer service and ground handling services for other airlines throughout its system. As of December 31, 2020, the Company had 601 total aircraft in its fleet, including 452 aircraft in scheduled service under its code-share agreements, summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CRJ200 CRJ700 CRJ900 E175 Total Delta 26 ​ 6 ​ 39 ​ 71 ​ 142 ​ United 104 ​ 19 ​ — ​ 90 ​ 213 ​ American — ​ 65 ​ — ​ — ​ 65 ​ Alaska — ​ — ​ — ​ 32 ​ 32 ​ Aircraft in scheduled service ​ 130 ​ 90 ​ 39 ​ 193 ​ 452 ​ Leased to third parties 2 ​ 34 ​ 5 ​ — ​ 41 ​ Other* 74 ​ 30 ​ 4 ​ — ​ 108 ​ Total Fleet 206 ​ 154 ​ 48 ​ 193 ​ 601 ​ *As of December 31, 2020, these aircraft have been removed from service and are in the process of being placed under a leasing arrangement with a third party, are aircraft transitioning between code-share agreements with the Company’s major airline partners and being used as a supplemental spare aircraft, or are in the process of being parted out. SkyWest Airlines has been a code-share partner with Delta since 1987, United since 1997, Alaska since 2011 and American since 2012. As of December 31, 2020, SkyWest Airlines operated as a Delta Connection carrier primarily in Salt Lake City, Detroit and Minneapolis, a United Express carrier primarily in Los Angeles, San Francisco, Denver, Houston, Chicago and the Pacific Northwest, an American carrier primarily in Chicago, Dallas, Los Angeles and Phoenix and an Alaska carrier primarily in the Pacific Northwest. SkyWest Airlines operates the following aircraft manufactured by Bombardier Aerospace (“Bombardier”): CRJ200s, CRJ700s and CRJ900s, and E175s manufactured by Embraer S.A. (“Embraer”). The CRJ200 is a single-class 50-seat aircraft. The CRJ700, CRJ900 E175 have seat Basis of Presentation The Company’s consolidated financial statements include the accounts of the Company and the SkyWest Airlines, ExpressJet (for the periods owned by the Company) and SkyWest Leasing segments, with all inter-company transactions and balances having been eliminated. In preparing the accompanying consolidated financial statements, the Company has reviewed, as determined necessary by the Company’s management, events that have occurred after December 31, 2020, through the filing date of the Company’s annual report with the U.S. Securities and Exchange Commission. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less to be cash equivalents. The Company had no restricted cash as of December 31, 2020 and 2019. Marketable Securities The Company’s investments in debt securities are classified as available-for-sale and are reported at fair market value with the net unrealized appreciation reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. At the time of sale, any realized appreciation or depreciation, calculated by the specific identification method, is recognized in other income and expense. At December 31, 2020 and 2019, the fair market value of the available-for-sale securities was the amortized cost. The Company’s position in marketable securities as of December 31, 2020 and 2019 was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross unrealized ​ Gross unrealized ​ ​ ​ ​ At December 31, 2020 Amortized Cost holding gains holding losses Fair market value Total cash and cash equivalents ​ $ 215,723 ​ $ — ​ $ — ​ $ 215,723 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bond and bond funds ​ $ 117,928 ​ $ — ​ $ — ​ $ 117,928 ​ Commercial Paper ​ 492,257 ​ — ​ — ​ 492,257 ​ Total marketable securities ​ $ 610,185 ​ $ — ​ $ — ​ $ 610,185 ​ Total assets measured at fair value ​ $ 825,908 ​ $ — ​ $ — ​ $ 825,908 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross unrealized ​ ​ Gross unrealized ​ ​ ​ ​ At December 31, 2019 Amortized Cost holding gains holding losses Fair market value Total cash and cash equivalents ​ $ 87,206 ​ $ — ​ $ — ​ $ 87,206 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bond and bond funds ​ $ 267,243 ​ $ — ​ $ — ​ $ 267,243 ​ Commercial Paper ​ 165,723 ​ — ​ — ​ 165,723 ​ Total marketable securities ​ $ 432,966 ​ $ — ​ $ — ​ $ 432,966 ​ Total assets measured at fair value ​ $ 520,172 ​ $ — ​ $ — ​ $ 520,172 ​ ​ Inventories Inventories include expendable parts, fuel and supplies and are valued at cost (FIFO basis) less an allowance for obsolescence based on historical results, excess parts and management’s expectations of future operations. Expendable inventory parts are charged to expense as used. An obsolescence allowance for flight equipment expendable parts is accrued based on estimated lives of the corresponding fleet types and salvage values. The inventory allowance as of December 31, 2020 and 2019 was $19.7 million and $15.9 million, respectively. Property and Equipment Property and equipment are stated at cost and depreciated over their useful lives to their estimated residual values using the straight-line method as follows: ​ ​ ​ Assets ​ Depreciable Life ​ Current Residual Value ​ Aircraft, rotable spares, and spare engines ​ up to 22 years up to 20 % ​ Ground equipment ​ up to 10 years 0 % ​ Office equipment ​ up to 7 years ​ 0 % ​ Leasehold improvements ​ Shorter of 15 years or lease term 0 % ​ Buildings ​ 20 - 39.5 years 0 % ​ Impairment of Long-Lived Assets As of December 31, 2020, the Company had approximately $5.4 billion of property and equipment and related assets. In accounting for these long-lived and intangible assets, the Company makes estimates about the expected useful lives of the assets, the expected residual values of certain of these assets, and the potential for impairment based on the fair value of the assets and the cash flows they generate. Factors indicating potential impairment include, but are not limited to, significant decreases in the market value of the long-lived assets, a significant change in the condition of the long-lived assets and operating cash flow losses associated with the use of the long-lived assets. On a periodic basis, the Company evaluates whether impairment indicators are present. When considering whether or not impairment of long- lived assets exists, the Company groups similar assets together at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities and compare the undiscounted cash flows for each asset group to the net carrying amount of the assets supporting the asset group. Asset groupings are done at the fleet or contract level. The Company did not recognize any impairment charges of long-lived assets during the years ended December 31, 2020, 2019 and 2018. Capitalized Interest Interest is capitalized on aircraft purchase deposits as a portion of the cost of the asset and is depreciated over the estimated useful life of the asset. During the years ended December 31, 2020, 2019 and 2018, the Company capitalized interest costs of approximately $1.7 million, $1.6 million, and $1.5 million, respectively. Maintenance The Company operates under a U.S. Federal Aviation Administration approved continuous inspection and maintenance program. The Company uses the direct expense method of accounting for its regional jet engine overhauls wherein the expense is recorded when the overhaul event occurs. The Company has engine services agreements with third-party vendors to provide long-term engine services covering the scheduled and unscheduled repairs for most of its aircraft. Under the terms of the agreements, the Company pays a fixed dollar amount per engine hour flown on a monthly basis and the third-party vendors will assume the responsibility to repair the engines at no additional cost to the Company, subject to certain specified exclusions. Maintenance costs under these contracts are recognized when the engine hour is flown pursuant to the terms of each contract. The costs of maintenance for airframe and avionics components, landing gear and other recurring maintenance are expensed as incurred. During the year ended December 31, 2020, the Company wrote-off $3.7 million of long-lived maintenance assets at maintenance locations the Company vacated during the year. Flying Agreements and Airport Customer Service and Other Revenues The Company recognizes flying agreements revenue and airport customer service and other revenues when the service is provided under its code-share agreements. Under the Company’s fixed-fee arrangements (referred to as “capacity purchase agreements”, “fixed-fee arrangements,” or “fixed-fee contracts”) with Delta, United, American and Alaska (each, a “major airline partner”), the major airline partner generally pays the Company a fixed-fee for each departure, flight hour (measured from takeoff to landing, excluding taxi time) or block hour (measured from takeoff to landing, including taxi time) incurred, and an amount per aircraft in service each month with additional incentives based on flight completion and on-time performance. The major airline partner also directly pays for or reimburses the Company for certain direct expenses incurred under the capacity purchase arrangement, such as fuel, airport landing fees and airport rents. Under the capacity purchase arrangements, the Company’s performance obligation is met and revenue is recognized when each flight is completed, measured in completed block hours, and is reflected in flying agreements revenue. The transaction price for the capacity purchase agreements is determined from the fixed-fee consideration, incentive consideration and directly reimbursed expenses earned as flights are completed over the agreement term. For the year ended December 31, 2020, capacity purchase arrangements represented approximately Under the Company’s prorate arrangements (referred to as a “prorate” or “revenue-sharing” arrangement), the major airline partner and the Company negotiate a passenger fare proration formula, pursuant to which the Company receives a percentage of the ticket revenues for those passengers traveling for one portion of their trip on a Company airline and the other portion of their trip on the major airline partner. Under the Company’s prorate flying agreements, the performance obligation is met and revenue is recognized when each flight is completed based upon the portion of the prorate passenger fare the Company anticipates that it will receive for each completed flight. The transaction price for the prorate agreements is determined from the proration formula derived from each passenger ticket amount on each completed flight over the agreement term. For the year ended December 31, 2020, prorate flying arrangements represented approximately Lease, airport services and other revenues primarily consist of ground handling functions, such as gate and ramp agent services at applicable airports where the Company provides such services. The transaction price for airport customer service agreements is determined from an agreed-upon rate by location applied to the applicable number of flights handled by the Company over the agreement term. Additionally, airport customer service and other revenues includes revenue generated from aircraft and spare engines leased to third parties. Of the Company’s $5.4 billion of property and equipment, net as of December 31, 2020, $271.1 million of regional jet aircraft and spare engines were leased to third parties under operating leases. The Company mitigates the residual asset risks of these assets by leasing aircraft and engine types that can be operated by the Company in the event of a default. A portion of the Company’s leases to third parties contain variable payments from lessees based on departures where the Company pays for maintenance. Additionally, the operating leases typically have specified lease return condition requirements paid by the lessee to the Company and the Company typically maintains inspection rights under the leases. ​ The following table represents the Company’s flying agreements revenue by type for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 2018 Capacity purchase agreements revenue: flight operations ​ $ 945,008 ​ $ 1,538,062 ​ $ 1,856,253 Capacity purchase agreements revenue: aircraft lease ​ 846,933 ​ 830,247 ​ 814,518 Prorate agreements revenue ​ 268,860 ​ 520,956 ​ 498,749 Flying agreements revenue ​ $ 2,060,801 ​ $ 2,889,265 ​ $ 3,169,520 ​ A portion of the Company’s compensation under its capacity purchase agreements is designed to reimburse the Company for certain aircraft ownership costs. The consideration for aircraft ownership costs varies by agreement but is intended to cover either the Company’s aircraft principal and interest debt service costs, its aircraft depreciation and interest expense or its aircraft lease expense costs while the aircraft is under contract. The consideration received for the use of the aircraft under the Company’s capacity purchase agreements is reflected as lease revenue, inasmuch as the agreements identify the “right of use” of a specific type and number of aircraft over a stated period of time. The lease revenue associated with the Company’s capacity purchase agreements is accounted for as an operating lease and is reflected as flying agreements revenue on the Company’s consolidated statements of comprehensive income. The Company has not separately stated aircraft rental income and aircraft rental expense in the consolidated statement of comprehensive income since the use of the aircraft is not a separate activity of the total service provided. Under the Company’s capacity purchase agreements, the Company is paid a fixed amount per month per aircraft over the contract term. The Company recognizes revenue attributed to the Fixed Monthly Payments proportionate to the number of block hours complete during each reporting period, relative to the estimated number of block hours we anticipate completing over the remaining contract term. Due to the material decrease in completed block hours in 2020 from historical levels and from anticipated future levels over the remaining contract terms, the Company determined the amount of Fixed Monthly Payments received in 2020 was disproportionately high relative to the number of block hours completed during 2020. The Company anticipates the future number of block hours it will complete over the remaining capacity purchase agreements will significantly increase from 2020 levels. Accordingly, the Company deferred recognizing revenue of $110.7 million of fixed monthly cash payments the Company received under its capacity purchase agreements during 2020. The Company’s deferred revenue related to the fixed payments will adjust over the remaining contract term for each capacity purchase agreement based on the number of block hours it completes each reporting period relative to the number of block hours it anticipates completing over the remaining contract term of each capacity purchase agreement. ​ In the event a flying agreement includes a mid-term rate reset to adjust rates prospectively and the contractual rates under the Company’s flying agreements have not been finalized at quarterly or annual financial statement dates, the Company applies the variable constraint guidance under Topic 606, where the Company records revenue to the extent it believes that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. ​ In several of the Company’s agreements, the Company is eligible to receive incentive compensation upon the achievement of certain performance criteria. The incentives are defined in the agreements and are measured and determined on a monthly, quarterly or semi-annual basis. At the end of each period during the term of an agreement, the Company calculates the incentives achieved during that period and recognizes revenue attributable to that agreement accordingly, subject to the variable constraint guidance under Topic 606. The following summarizes the significant provisions of each code-share agreement the Company has with each major airline partner through SkyWest Airlines: Delta Connection Agreements Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates Delta Connection Agreement (capacity purchase arrangement) ​ ● E175 ● CRJ 900 ● CRJ 700 ​ 71 39 6 ​ ● Individual aircraft have scheduled removal dates from 2021 to 2030 ● ​ Delta Connection Prorate Agreement (prorate arrangement) ​ ● CRJ 200 ​ 26 ​ ● Terminable with 30-day ​ ​ United Express Agreements ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates United Express Agreements (capacity purchase arrangement) ​ ● E175 ● CRJ 700 ● CRJ 200 ​ 90 19 70 ​ ​ ● Individual aircraft have scheduled removal dates under the agreement between 2022 and 2029 ● ​ United Express Prorate Agreement (prorate arrangement) ​ ● CRJ 200 ​ ​ 34 ​ ● Terminable with 120-day ​ ​ American Capacity Purchase Agreement ​ ​ ​ ​ ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates American Agreement (capacity purchase arrangement) ​ ● CRJ 700 ​ ​ 65 ​ ● ● ​ ​ Alaska Capacity Purchase Agreement ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates Alaska Agreement (capacity purchase arrangement) ​ ● E175 ​ ​ 32 ​ ● ● ​ ​ In addition to the contractual arrangements described above, as of December 31, 2020, SkyWest Airlines entered into a capacity purchase agreement with American to place 20 E175 aircraft into service. The delivery dates for the 20 new E175 aircraft are currently scheduled for 2021 and 2022 and the aircraft are expected to be placed into service in 2022. SkyWest Airlines also entered into an agreement with American to place 25 used CRJ700s under a multi-year capacity purchase agreement beginning in 2021. Final delivery dates may be adjusted based on various factors. ​ SkyWest Airlines also entered into an agreement with Delta to place one CRJ900 aircraft under a capacity purchase agreement in 2021. The Company anticipates Delta will acquire the aircraft and SkyWest operate the aircraft. ​ When an aircraft is scheduled to be removed from a capacity purchase arrangement, the Company may, as practical under the circumstances, negotiate an extension with the respective major airline partner, negotiate the placement of the aircraft with another major airline partner, return the aircraft to the lessor if the aircraft is leased and the lease is expiring, place owned aircraft for sale, or pursue other uses for the aircraft. Other uses for the aircraft may include placing the aircraft in a prorate arrangement, leasing the aircraft to a third party or parting out the aircraft to use the engines and parts as spare inventory or to lease the engines to a third party. ​ The following table represents the Company’s lease, airport services and other revenues for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 2018 Airport customer service and other revenue ​ $ 25,804 ​ $ 45,538 ​ $ 48,236 Operating lease income relating to lease payments ​ 34,791 ​ 27,552 ​ 3,923 Operating lease income relating to variable lease payments ​ 5,710 ​ 9,608 ​ — Lease, airport services and other ​ $ 66,305 ​ $ 82,698 ​ $ 52,159 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 $ 43,573 2022 ​ 43,390 ​ 2023 ​ 42,837 ​ 2024 ​ 42,530 ​ 2025 ​ 39,082 ​ Thereafter ​ 155,089 ​ ​ ​ $ 366,501 ​ ​ The Company’s operating revenues could be impacted by a number of factors, including changes to the Company’s code-share agreements with its major airline partners, changes in flight schedules, contract modifications resulting from contract renegotiations, the Company’s ability to earn incentive payments contemplated under the Company’s code-share agreements and settlement of reimbursement disputes with the Company’s major airline partners. ​ Other ancillary revenues commonly associated with airlines, such as baggage fee revenue, ticket change fee revenue and the marketing component of the sale of mileage credits, are retained by the Company’s major airline partners on flights that the Company operates under its code-share agreements. ​ As of December 31, 2020, the Company had $34.5 million in accounts receivable of which $27.5 million related to flying agreements. As of December 31, 2019, the Company had $83.0 million in accounts receivable of which $58.8 million related to flying agreements. ​ Allowance for Credit Losses The Company monitors publicly available credit ratings for entities for which the Company has a significant receivable balance. As of December 31, 2020, the Company had gross receivables of $56.1 million in current assets and gross receivables of $157.4 million in other long-term assets. The Company has established credit loss reserves based on publicly available historic default rates issued by a third party for companies with similar credit ratings, factoring in the term of the respective accounts receivable or note receivable. During the twelve months ended December 31, 2020, the collectability on a note receivable from Kair Enterprises, Inc. associated with the Company’s sale of ExpressJet in 2019 became uncertain due to ExpressJet ceasing operations during the year and the credit ratings were lowered on certain entities for which the Company has outstanding accounts receivable or notes receivable, which were the primary drivers for the increase in the Company’s credit loss reserve when benchmarked against historic default rates as of January 1, 2020, when the Company adopted Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments” (“Topic 326”) . The following table summarizes the changes in allowance for credit losses: ​ ​ ​ ​ ​ Allowance for Credit Losses Balance at January 1, 2020 ​ $ 15,388 Additions to credit loss reserves ​ 30,837 Write-offs charged against allowance ​ — Balance at December 31, 2020 ​ $ 46,225 ​ Income Taxes The Company recognizes a net liability or asset for the deferred tax consequences of all temporary differences between the tax basis of assets and liabilities and their reported amounts in the consolidated financial statements that are expected to result in taxable or deductible amounts in future years when the reported amounts of the assets and liabilities are recovered or settled. Net Income (Loss) Per Common Share Basic net income (loss) per common share (“Basic EPS”) excludes dilution and is computed by dividing net income by the weighted average number of common shares outstanding during the period. Diluted net income per common share (“Diluted EPS”) reflects the potential dilution that could occur if stock options or other contracts to issue common stock were exercised or converted into common stock. The computation of Diluted EPS does not assume exercise or conversion of securities that would have an anti-dilutive effect on net income (loss) per common share. During the year ended December 31, 2020, 1,074,375 shares reserved for the issuance of employee equity awards and warrants to acquire the Company’s common stock were excluded in the computation of Diluted EPS since the Company reported a net loss for the year ended December 31, 2020. During the year ended December 31, 2019, 150,000 performance share units (at target performance) were excluded in the computation of Diluted EPS since the Company had not achieved the minimum target thresholds as of December 31, 2019. During the year ended December 31, 2018, 207,000 performance share units (at target performance) were excluded in the computation of Diluted EPS since the Company had not achieved the minimum target thresholds as of December 31, 2018. The calculation of the weighted average number of common shares outstanding for Basic EPS and Diluted EPS are as follows for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Numerator: ​ ​ ​ ​ Net income (loss) ​ $ (8,515) ​ $ 340,099 ​ $ 280,372 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic earnings per share weighted average shares ​ 50,195 ​ 50,932 ​ 51,914 ​ Dilution due to stock options and restricted stock units ​ — ​ 443 ​ 957 ​ Diluted earnings per share weighted average shares ​ 50,195 ​ 51,375 ​ 52,871 ​ Basic earnings (loss) per share ​ $ (0.17) ​ $ 6.68 ​ $ 5.40 ​ Diluted earnings (loss) per share ​ $ (0.17) ​ $ 6.62 ​ $ 5.30 ​ Comprehensive Income (Loss) Comprehensive income (loss) includes charges and credits to stockholders’ equity that are not the result of transactions with the Company’s shareholders, including changes in unrealized appreciation on marketable debt securities. Fair Value of Financial Instruments The carrying amounts reported in the consolidated balance sheets for receivables and accounts payable approximate fair values because of the immediate or short-term maturity of these financial instruments. Marketable securities are reported at fair value based on market quoted prices in the consolidated balance sheets. If quoted prices in active markets are no longer available, the Company has estimated the fair values of these securities utilizing a discounted cash flow analysis. These analyses consider, among other items, the collateralization underlying the security investments, the creditworthiness of the counterparty, the timing of expected future cash flows, and the expectation of the next time the security is expected to have a successful auction. The fair value of the Company’s long-term debt is estimated based on current rates offered to the Company for similar debt and was approximately $3,244.0 million as of December 31, 2020, as compared to the carrying amount of $3,236.0 million as of December 31, 2020. The Company’s fair value of long-term debt as of December 31, 2019 was $3,049.1 million as compared to the carrying amount of $3,017.5 million as of December 31, 2019. Segment Reporting Generally accepted accounting principles require disclosures related to components of a company for which separate financial information is available to, and regularly evaluated by, the Company’s chief operating decision maker when deciding how to allocate resources and in assessing performance. The Company’s three operating segments (prior to the sale of ExpressJet in January 2019) consist of the operations conducted by SkyWest Airlines, ExpressJet (for the periods owned by the Company) and SkyWest Leasing. Following the sale of ExpressJet, the Company has two reportable segments: SkyWest Airlines and SkyWest Leasing. Information pertaining to the Company’s reportable segments is presented in Note 3, Segment Reporting ​ Recent Accounting Pronouncements Recently Adopted Standards In June 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments” (“Topic 326”), which requires measurement and recognition of expected credit losses for financial assets held and requires enhanced disclosure regarding significant estimates and judgments used in estimating credit losses. Topic 326 is effective for the Company beginning January 1, 2020. The Company adopted Topic 326 on January 1, 2020. The Company’s primary financial assets as of December 31, 2019 included trade receivables from its flying agreements, a note receivable from the sale of ExpressJet, and receivables from aircraft manufacturers and other third parties in the airline industry. The Company recorded a credit loss of

Impact of the COVID-19 Pandemic

Impact of the COVID-19 Pandemic	12 Months Ended
	Dec. 31, 2020
Impact of the COVID-19 Pandemic
Impact of the COVID-19 Pandemic	(2) Impact of the COVID-19 Pandemic COVID-19, which was declared a global health pandemic by the World Health Organization in March 2020, has continued to spread around the world and driven the implementation and continuation of significant, government-imposed measures to prevent or reduce its spread, including travel restrictions, closing of borders, “shelter in place” orders and business closures. Consequently, the Company and its major airline partners, have experienced an unprecedented decline in the demand for air travel, which has materially and adversely affected the Company’s revenues, particularly under its prorate arrangements. The continued spread of the virus and the ongoing global pandemic has affected nearly all of the domestic and international networks of the Company’s major airline partners for whom it conducts flight operations and relies on to set its flight schedules. While the length and severity of the reduction in demand due to COVID-19 are uncertain, the Company presently expects a continued significant negative impact on its results of operations at a minimum through 2021. ​ In response to these developments, the Company has implemented measures to focus on the personal safety of its passengers and employees, while at the same time seeking to mitigate the impact on the Company’s financial position and operations. These measures include, but are not limited to, the following: ​ Focus on the Personal Safety of Passengers and Employees. ​ ● Working with the Company’s major airline partners to enhance its aircraft cleaning procedures. ● Working with the Company’s major airline partners to provide masks for crewmembers and ensuring that all fleet service personnel have the necessary personal protective equipment for disinfecting the aircraft. ● Providing a number of options to employees who are diagnosed with COVID-19, including pay protection and extended leave options. ● Implementing workforce social distancing and protection measures, and enhanced cleaning of the Company’s facilities, including training facilities, using methods and products similar to what the Company is using on its aircraft. ​ Capacity Reductions. scheduled flights. Therefore, in response to this decreased demand, the Company has significantly reduced its capacity. During the year ended December 31, 2020, the Company’s number of departures and block hours each decreased 30.5% and 33.5%, respectively, from the year ended December 31, 2019. The number of daily scheduled flights operated by the Company may not return to pre-COVID-19 levels by the end of 2021 or possibly thereafter. The Company will continue to work with its major airline partners regarding future schedules and make demand-driven adjustments to its capacity as needed. The Company removed 55 CRJ200 aircraft that were operating under the SkyWest Airlines Delta Connection Agreement as a result of contract expirations that were not extended during the 2020 calendar year. The Company additionally terminated its American Prorate Agreement on seven CRJ200 aircraft in the second quarter of 2020 and the Company may have further reductions in the number of CRJ200 aircraft operating under its other prorate agreements. The Company may receive requests by its major airline partners to defer deliveries of new or used aircraft that were previously scheduled for delivery in 2021 and 2022. ​ Cost Reductions. ​ ● Reducing employee-related costs including by: o Offering voluntary unpaid leave to employees. o Suspending all non-scale pay increases. o Instituting a company-wide hiring freeze. ● Delaying non-essential projects and reducing or suspending other discretionary spending. ​ Liquidity. ​ CARES Act. ​ In April 2020, SkyWest Airlines entered into an agreement with Treasury to receive $438.0 million in emergency relief through the CARES Act payroll support program to be paid in installments from April to September 2020, which was amended and increased to $450.7 million. SkyWest Airlines received the $450.7 million in the aggregate under the payroll support program during the year ended December 31, 2020. The relief payments are conditioned on the Company’s agreement to, among other things, refrain from conducting involuntary employee layoffs or furloughs through September 30, 2020. Other conditions include bans on share repurchases and dividends through September 30, 2021, continuing essential air service as directed by the U.S. Department of Transportation and certain limitations on executive compensation. The relief payments received under the CARES Act payroll support program included $345.5 million in a grant and $105.2 million in an unsecured 10-year loan. The loan bears interest at an annual rate of 1.00% for the first five years (through April 2025) and the Secured Overnight Financing Rate plus 2.00% in the final five years. In return, the Company issued to Treasury warrants to purchase 370,720 shares of the Company’s common stock. These warrants have an exercise price of $28.38 per share and a five-year term from the date of issuance. ​ The relative fair value of the warrants is recorded within stockholder's equity and as a discount reducing the carrying value of the loan, which will be amortized as interest expense in the Company’s income statement over the term of the loan. The proceeds of the grant are recorded in cash and cash equivalents when received and will be recognized as a reduction in expense in CARES Act payroll support grant in our income statement over the periods that the funds are intended to compensate. ​ During the year ended December 31, 2020, the Company recognized $345.5 million of grant proceeds received under the CARES Act payroll support program, as a reduction in payroll expense. See Note 4, "Long-Term Debt," for further discussion of the unsecured loans and warrants to acquire the Company’s shares issued under the CARES Act payroll support program. ​ The CARES Act also provides for up to $25 billion in secured loans to the airline industry. In September 2020 the Company entered into a secured loan and guarantee agreement with Treasury (the “Treasury Loan Agreement”), which permits the Company to borrow up to $573 million. Subsequently, on October 28, 2020, the Company entered into an amendment to the Treasury Loan Agreement that permits the Company to borrow up to $725 million in the aggregate. As of December 31, 2020, the Company has borrowed $60 million and may, at its option, borrow additional amounts in up to two subsequent borrowings until May 28, 2021. The proceeds are to be used for certain general corporate purposes and operating expenses in accordance with the terms and conditions of the Treasury Loan Agreement and the applicable provisions of the CARES Act. The loan will bear interest at a variable rate per annum equal to the London interbank offer rate divided by one minus the Eurodollar Reserve Percentage (as defined in the Treasury Loan Agreement) plus 3.00%. The applicable interest rate for the $60 million loan will be 3.22% per annum through September 15, 2021 at which time the interest rate will reset in accordance with the foregoing formula. In return, the Company agreed to issue to Treasury warrants to purchase shares of the Company’s common stock based on a debt coverage ratio and amounts drawn under the facility. The Company issued warrants to purchase 211,416 shares of the Company’s common stock to Treasury in conjunction with the Company’s $60 million borrowing under the facility. These warrants have an exercise price of $28.38 per share and a five-year term from the date of issuance. ​

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2020
Segment Reporting
Segment Reporting	(3) Segment Reporting Generally accepted accounting principles require disclosures related to components of a company for which separate financial information is available to, and regularly evaluated by, the Company’s chief operating decision maker when deciding how to allocate resources and in assessing performance. Prior to the Company’s sale of ExpressJet on January 22, 2019, the Company’s three reporting segments consisted of the operations of SkyWest Airlines, ExpressJet and SkyWest Leasing activities. The segment information presented for ExpressJet reflects the period of time prior to the sale, when ExpressJet was operating as a subsidiary of the Company. ​ The Company’s chief operating decision maker analyzes the profitability of operating new aircraft financed through the issuance of debt, including the Company’s E175 fleet, separately from the profitability of the Company’s capital deployed for ownership and financing of such aircraft. The SkyWest Airlines segment includes revenue earned under the applicable capacity purchase contracts attributed to operating such aircraft and the respective operating costs. The SkyWest Leasing segment includes applicable revenue earned under the applicable capacity purchase contracts attributed to the ownership of new aircraft acquired through the issuance of debt and the respective depreciation and interest expense of such aircraft. The SkyWest Leasing segment also includes the activity of leasing regional jet aircraft and spare engines to third parties. The SkyWest Leasing segment’s total assets and capital expenditures include new aircraft acquired through the issuance of debt and assets leased to third parties. ​ The following represents the Company’s segment data for the years ended December 31, 2020, 2019 and 2018 (in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ SkyWest ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Airlines ​ ​ SkyWest Leasing ​ ​ Consolidated ​ Operating revenues ​ $ 1,636,762 ​ $ 490,344 ​ $ 2,127,106 ​ Operating expense ​ 1,716,808 ​ ​ 301,496 ​ ​ 2,018,304 ​ Depreciation and amortization expense ​ 221,216 ​ 253,743 ​ 474,959 ​ Interest expense ​ 12,381 ​ 110,792 ​ 123,173 ​ Segment profit (loss) (1) ​ (92,427) ​ 78,056 ​ (14,371) ​ Total assets ​ 2,804,259 ​ 4,083,363 ​ 6,887,622 ​ Capital expenditures (including non-cash) ​ 124,825 ​ 335,658 ​ 460,483 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ SkyWest ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Airlines ​ ​ ExpressJet ​ ​ SkyWest Leasing ​ ​ Consolidated Operating revenues ​ $ 2,478,681 ​ $ 24,050 ​ $ 469,232 ​ $ 2,971,963 ​ Operating expense ​ 2,214,632 ​ ​ 28,690 ​ ​ 216,383 ​ 2,459,705 ​ Depreciation and amortization expense ​ 168,246 ​ 971 ​ 198,881 ​ 368,098 ​ Special items ​ ​ 18,508 ​ ​ 3,361 ​ ​ — ​ ​ 21,869 ​ Interest expense ​ 13,525 ​ — ​ 114,230 ​ 127,755 ​ Segment profit (loss) (1) ​ 250,524 ​ (4,640) ​ 138,619 ​ 384,503 ​ Total assets ​ 2,728,964 ​ — ​ 3,928,165 ​ 6,657,129 ​ Capital expenditures (including non-cash) ​ 270,191 ​ — ​ 576,279 ​ 846,470 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2018 ​ ​ ​ ​ SkyWest ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Airlines ​ ​ ExpressJet ​ ​ SkyWest Leasing ​ ​ Consolidated Operating revenues ​ $ 2,346,251 ​ $ 564,202 ​ $ 311,226 ​ $ 3,221,679 ​ Operating expense ​ 2,022,560 ​ ​ 577,608 ​ ​ 147,231 ​ 2,747,399 ​ Depreciation and amortization expense ​ 155,511 ​ 37,290 ​ 141,788 ​ 334,589 ​ Interest expense ​ 17,021 ​ 2,340 ​ 101,048 ​ 120,409 ​ Segment profit (loss) (1) ​ 306,670 ​ (15,746) ​ 62,947 ​ 353,871 ​ Total assets ​ 2,531,707 ​ 279,303 ​ 3,502,202 ​ 6,313,212 ​ Capital expenditures (including non-cash) ​ 149,731 ​ 10,137 ​ 996,408 ​ 1,156,276 ​ (1) Segment profit is operating income less interest expense

Long-term Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2020
Long-term Debt
Long-term Debt	(4) Long-term Debt Long-term debt consisted of the following as of December 31, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Notes payable to a financing company, due in semi-annual installments, with a fixed interest rate of 3.25% through 2021, secured by aircraft ​ $ 6,205 ​ $ 18,412 ​ Notes payable to banks, due in semi-annual installments plus interest at 6.24% to 6.51% through 2021, secured by aircraft ​ 7,608 ​ 22,557 ​ Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.68% to 6.86% through 2029, secured by aircraft ​ 424,407 ​ 438,878 ​ Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.08% through 2032, secured by aircraft ​ ​ 2,618,777 ​ ​ 2,537,676 ​ Notes payable to bank, due in monthly installments interest based on LIBOR plus interest spread at 2.65% through 2021 ​ ​ 13,795 ​ ​ — ​ Notes payable to US Government, interest due quarterly based on LIBOR plus interest spread currently at 3.22% through 2025, secured by parts and engines ​ ​ 60,000 ​ ​ — ​ Notes payable to US Government, interest due quarterly at 1.00% through 2025 and based on SOFR plus spread from 2025 through 2030, unsecured ​ 105,210 ​ — ​ Long-term debt ​ $ 3,236,002 ​ $ 3,017,523 ​ Current portion of long-term debt ​ (406,005) ​ (367,954) ​ Less long-term portion of unamortized debt issue cost, net ​ ​ (28,459) ​ ​ (20,580) ​ Long-term debt, net of current maturities and debt issue costs ​ $ 2,801,538 ​ $ 2,628,989 ​ ​ ​ ​ ​ ​ ​ ​ ​ Current portion of long-term debt ​ 406,005 ​ 367,954 ​ Less current portion of unamortized debt issue cost, net ​ ​ (3,847) ​ ​ (3,828) ​ Current portion of long-term debt, net of debt issue costs ​ $ 402,158 ​ $ 364,126 ​ ​ During 2020, the Company took delivery of six new E175 aircraft that the Company financed through $107.7 million of long-term debt. The debt associated with the six E175 aircraft has a 12-year ​ During 2020, the Company took delivery of 21 used CRJ700 aircraft that the Company financed through $133.5 million of long-term debt. The debt associated with the 10 of the CRJ700 aircraft has a 7.5-year term, is due in quarterly installments with fixed annual interest rates of 3.5% and is secured by the CRJ700 aircraft. The debt associated with 11 of the CRJ700 aircraft has a 5-year term, is due in monthly installments with fixed annual interest rates of 4.0% and is secured by the CRJ700 aircraft. ​ During 2020, in connection with the CARES Act payroll support program, the Company issued to Treasury a promissory note for an aggregate principal amount of $105.2 million and issued warrants to purchase 370,720 shares of the Company’s common stock. The Company has recorded the value of the promissory note and warrants on a relative fair value basis as $105.2 million of long-term debt and $5.0 million in common stock, respectively. These warrants have an exercise price of $28.38 per share and a five-year term from the date of issuance. ​ Additionally, during 2020, in connection with the CARES Act, the Company entered into the Treasury Loan Agreement with Treasury which permits the Company to borrow up to $573 million. Subsequently, on October 28, 2020, the Company entered into an amendment to the Treasury Loan Agreement that permits the Company to borrow up to $725 million in the aggregate. As of December 31, 2020, the Company has drawn $60 million under the agreement and issued warrants to purchase 211,416 shares of the Company’s common stock. The Treasury Loan Agreement is secured by aircraft engines and aircraft parts. The Company may, at its option, borrow additional amounts in up to two subsequent borrowings until May 28, 2021. The proceeds will be used for certain general corporate purposes and operating expenses in accordance with the terms and conditions of the Treasury Loan Agreement and the applicable provisions of the CARES Act. The Company has recorded the value of the promissory note and warrants on a relative fair value basis as $60 million of long-term debt and $3.2 million in common stock, respectively. These warrants have an exercise price of $28.38 per share and a five-year term from the date of issuance. As of December 31, 2020, and 2019, the Company had $3.07 billion and $3.02 billion, respectively, of long-term debt obligations primarily related to the acquisition of aircraft and certain spare engines. The average effective interest rate on the debt related to those long-term debt obligations at December 31, 2020 and 2019, was approximately 4.0% and 4.2%, respectively. During the year ended December 31, 2019, the Company used $30.1 million in cash to extinguish $30.1 million in debt early. These payments did not result in a pre-tax gain or loss in the consolidated statements of comprehensive income (loss). The aggregate amounts of principal maturities of long-term debt as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ 2021 $ 406,005 2022 ​ 407,554 ​ 2023 ​ 418,048 ​ 2024 ​ 372,322 ​ 2025 ​ 447,251 ​ Thereafter ​ 1,184,822 ​ ​ ​ $ 3,236,002 ​ ​ As of December 31, 2020 and 2019, SkyWest Airlines had a $75 million line of credit. The line of credit includes minimum liquidity and profitability covenants and is secured by certain assets. As of December 31, 2020, the Company obtained waivers for the line of credit agreement that permitted the Company to receive funding under the CARES Act and waived compliance with minimum profitability covenants through June 30, 2021. As of December 31, 2020 and 2019, SkyWest Airlines had no amount outstanding under the line of credit facility. However, at December 31, 2020 and 2019 the Company had $35.5 million and $8.8 million, respectively, in letters of credit issued under the facility which reduced the amount available under the facility to $39.5 million and $66.2 million, respectively. The facility expires on September 1, 2021 and has a variable interest rate of LIBOR plus 2.5% at December 31, 2020. ​ As of December 31, 2020 and 2019, the Company had $61.1 million and $61.7 million, respectively, in letters of credit and surety bonds outstanding with various banks and surety institutions in addition to the letters of credit outstanding under the line of credit.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Taxes
Income Taxes	(5) Income Taxes The provision for income taxes includes the following components (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Current tax provision (benefit): ​ ​ ​ ​ Federal ​ $ (4,397) ​ $ (4,395) ​ $ (21,598) ​ State ​ (875) ​ 891 ​ 1,465 ​ Foreign ​ ​ — ​ ​ — ​ ​ 1,575 ​ ​ ​ (5,272) ​ (3,504) ​ (18,558) ​ Deferred tax provision (benefit): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ 6,659 ​ 95,655 ​ 92,250 ​ State ​ (199) ​ 14,055 ​ 12,250 ​ ​ ​ 6,460 ​ 109,710 ​ 104,500 ​ Provision (benefit) for income taxes ​ $ 1,188 ​ $ 106,206 ​ $ 85,942 ​ ​ The following is a reconciliation between a federal income tax rate of 21% and the effective tax rate which is derived by dividing the provision for income taxes by the income (loss) before the provision for income taxes (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Computed provision for income taxes at the statutory rate $ (1,539) $ 93,724 $ 76,926 ​ Increase (decrease) in income taxes resulting from: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ State income tax provision, net of federal income tax benefit ​ 173 ​ 15,645 ​ 12,711 ​ Non-deductible expenses ​ ​ 2,539 ​ ​ 3,934 ​ ​ 1,956 ​ Valuation allowance changes affecting the provision for income taxes ​ (892) ​ (517) ​ (1,187) ​ Foreign income taxes, net of federal & state benefit ​ ​ — ​ ​ — ​ ​ 1,192 ​ Excess tax benefits from share-based compensation ​ ​ (1,434) ​ ​ (3,525) ​ ​ (4,548) ​ Other, net ​ 2,341 ​ (3,055) ​ (1,108) ​ Provision for income taxes ​ $ 1,188 ​ $ 106,206 ​ $ 85,942 ​ ​ For the year ended December 31, 2020, the Company released $0.9 million of valuation allowance against certain deferred tax assets primarily associated with state net operating losses with a limited carry forward period. For the year ended December 31, 2019, the Company released $0.5 million of valuation allowance against certain deferred tax assets primarily associated with ExpressJet state net operating losses. For the year ended December 31, 2018, the Company released ​ The Company recorded a $1.4 million, $3.5 million and $4.5 million benefit from share-based compensation in 2020, 2019, and 2018, respectively, relating to ASU 2016-09 which, requires excess tax benefits and deficiencies to be recognized in the income tax provision during the period stock options are exercised and when stock awards vest. ​ The significant components of the Company’s net deferred tax assets and liabilities as of December 31, 2020 and 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2020 ​ 2019 Deferred tax assets: ​ ​ ​ Accrued benefits ​ $ 19,668 ​ $ 20,848 ​ Net operating loss carryforward ​ 229,815 ​ 358,685 ​ AMT credit carryforward ​ — ​ 4,397 ​ Aircraft credits ​ 12,765 ​ 9,114 ​ Deferred revenue ​ ​ 27,076 ​ ​ — ​ Accrued reserves and other ​ 34,816 ​ 17,225 ​ Total deferred tax assets ​ 324,140 ​ 410,269 ​ Valuation allowance ​ — ​ (892) ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Accelerated depreciation ​ (950,071) ​ (1,032,957) ​ Total deferred tax liabilities ​ (950,071) ​ (1,032,957) ​ Net deferred tax liability ​ $ (625,931) ​ $ (623,580) ​ ​ ​ At %, respectively. The Company anticipated that the federal and state net operating losses will start to expire in 2036 and 2021, respectively. As of December 31, 2019, the Company also had an alternative minimum tax credit of approximately $4.4 million, which did not expire. Under the CARES Act of 2020, these credits were realized by claiming a refundable credit during 2020. The Company has no ongoing federal or state examinations. ​ Under ASC Topic 740, the accounting guidance related to uncertainty in tax positions requires that the impact of a tax position be recognized in the financial statements if that position is more likely than not of being sustained on audit, based on the technical merits of the position. A reconciliation of the beginning and ending amount of unrecognized tax benefits for the year ended December 31, 2020, 2019 and 2018 is as follows (in thousands) : ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Unrecognized tax benefits at the beginning of year $ 14,620 $ 14,553 $ 2,223 Gross increases - current year tax positions ​ ​ — ​ ​ — ​ ​ 13,899 Gross increases - prior year tax positions ​ 360 ​ 67 ​ — Gross decreases - prior year tax positions ​ ​ — ​ ​ — ​ ​ (1,569) Unrecognized tax benefits at end of year ​ $ 14,980 ​ $ 14,620 ​ $ 14,553 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and penalties in year-end balance ​ $ 427 ​ $ 67 ​ $ — ​ For the years ending December 31, 2020 and 2019, the Company recorded $360,000 and $67,000, respectively, of interest expense related to uncertain tax positions not offset by the Company's tax attributes.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies
Commitments and Contingencies	(6) Commitments and Contingencies Self-Insurance The Company self-insures a portion of its potential losses from claims related to workers’ compensation, environmental issues, property damage, medical insurance for employees and general liability. Losses are accrued based on an estimate of the ultimate aggregate liability for claims incurred, using standard industry practices and the Company’s actual experience. The Company uses judgment and estimates in determining the ultimate aggregate liabilities for claims incurred in its workers’ compensation liability. The Company also used significant assumptions in determining the workers compensation liability such as an estimation of loss payment and loss reporting development patterns. At December 31, 2020 and 2019, the Company’s accrued workers’ compensation liability totaled $20.7 million and $23.9 million, respectively. Actual results could differ from these estimates. Legal Matters The Company is subject to certain legal actions which it considers routine to its business activities. As of December 31, 2020, management believed, after consultation with legal counsel, that the ultimate outcome of such legal matters was not likely to have a material adverse effect on the Company’s financial position, liquidity or results of operations. Concentration Risk and Significant Customers The Company requires no collateral from its major airline partners or customers, but monitors the financial condition of its major airline partners. Under the majority of the Company’s code-share agreements, the Company receives weekly payments from its major code-share partners that approximate a significant percentage of the compensation earned for such period. Additionally, the Company provides certain customer service functions at multiple airports for various airlines and the Company maintains a credit loss reserve based upon expected collectability of all accounts receivable. For the years ended December 31, 2020, 2019 and 2018, the Company’s contractual relationships with Delta and United combined accounted for approximately 76.4%, 77.6% and 81.4%, respectively of the Company’s total revenues. Employees Under Collective Bargaining Agreements As of December 31, 2020, the Company had approximately 12,502 full- time equivalent employees. Although Aircraft Purchase Commitments As of December 31, 2020, the Company had a purchase commitment to purchase 20 new E175 aircraft in late 2021 and early 2022. Subsequent to December 31, 2020, the Company entered into a purchase commitment to purchase 12 used CRJ700 aircraft in 2021.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases
Leases	(7) Leases Effective January 1, 2019, the Company adopted Topic 842. The Company leases property and equipment under operating leases. For leases with durations longer than 12 months, the Company recorded the related operating lease right-of-use asset and operating lease liability at the present value of lease payments over the term. The Company used its incremental borrowing rate to discount the ​ Aircraft As of December 31, 2020, excluding aircraft financed by our major partners that we operate for them under contract, the Company had 41 aircraft under long-term lease agreements with remaining terms ranging from less than one year to ten years. ​ With the adoption of Topic 842, the Company evaluated whether leased aircraft asset groups within the Company’s fleet were impaired. Under the transition guidance for Topic 842, a company is permitted to recognize a previously unrecognized impairment related to a right-of-use asset in the period prior to the adoption date of Topic 842 if the event giving rise to the impairment occurred before the adoption date. In 2016, the Company recorded an impairment on certain of its long-lived assets, which included the Company’s CRJ200 aircraft . In 2016, the market lease rate was less than the contractual lease rate on the Company’s CRJ200 leased aircraft. The Company recorded an impairment of ​ Airport facilities The Company has operating leases for facility space including airport terminals, office space, cargo warehouses and maintenance facilities. The Company generally leases this space from government agencies that control the use of the airport. The remaining lease terms for facility space vary from one month to 36 years. The Company’s operating leases with lease rates that are variable based on airport operating costs, use of the facilities or other variable factors are excluded from the Company’s right-of-use assets and operating lease liabilities in accordance with accounting guidance. ​ Leases As of December 31, 2020, the Company’s right-of-use assets were $282.4 million, the Company’s current maturities of operating lease liabilities were $82.6 million, and the Company’s noncurrent lease liabilities were $205.8 million. During 2020, the Company paid $90.3 million in operating leases reflected as a reduction from operating cash flows. ​ The table below presents lease related terms and discount rates as of December 31, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2020 Weighted-average remaining lease term ​ Operating leases ​ ​ 6.50 years ​ Weighted-average discount rate ​ ​ ​ Operating leases ​ ​ 6.1% ​ ​ The Company’s lease costs for 2020 and 2019 included the following components (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 Operating lease cost $ 94,915 $ 104,011 Variable and short-term lease cost ​ 4,619 ​ 5,232 Sublease income ​ ​ (6,304) ​ ​ (1,436) Total lease cost $ 93,230 $ 107,807 ​ As of December 31, 2020, the Company leased aircraft, airport facilities, office space, and other property and equipment under non-cancelable operating leases, which are generally on a long-term, triple-net lease basis pursuant to which the Company pays taxes, maintenance, insurance and certain other operating expenses applicable to the leased property. The Company expects that, in the normal course of business, such operating leases that expire will be renewed or replaced by other leases, or the property may be purchased rather than leased. ​ ​ ​ ​ ​ ​ 2021 $ 85,869 2022 ​ 77,780 ​ 2023 ​ 69,530 ​ 2024 ​ 28,091 ​ 2025 ​ 15,751 ​ Thereafter ​ 82,719 ​ ​ ​ $ 359,740 ​ ​ Total rental expense for non-cancelable aircraft operating leases was approximately $65.3 million, $72.0 million and $154.9 million for the years ended December 31, 2020, 2019 and 2018, respectively. The minimum rental expense for airport station rents was approximately $20.1 million, $23.1 million and $19.6 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Measurements
Fair Value Measurements	(8) Fair Value Measurements The Company holds certain assets that are required to be measured at fair value in accordance with GAAP. The Company determined fair value of these assets based on the following three levels of inputs: ​ Level 1 Level 2 Level 3 ​ As of December 31, 2020, the Company held certain assets that are required to be measured at fair value on a recurring basis. Assets measured at fair value on a recurring basis are summarized below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of December 31, 2020 ​ ​ Total Level 1 Level 2 Level 3 Marketable Securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bonds and bond funds ​ $ 117,928 ​ $ — ​ $ 117,928 ​ $ — ​ Commercial paper ​ 492,257 ​ — ​ 492,257 ​ — ​ ​ ​ $ 610,185 ​ $ — ​ $ 610,185 ​ $ — ​ Cash, Cash Equivalents and Restricted Cash ​ ​ 215,723 ​ 215,723 ​ — ​ — ​ Total Assets Measured at Fair Value ​ $ 825,908 ​ $ 215,723 ​ $ 610,185 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of December 31, 2019 ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Marketable Securities ​ ​ ​ ​ ​ Bonds and bond funds ​ $ 267,243 ​ $ — ​ $ 267,243 ​ $ — ​ Commercial paper ​ 165,723 ​ — ​ 165,723 ​ — ​ ​ ​ $ 432,966 ​ $ — ​ $ 432,966 ​ $ — ​ Cash, Cash Equivalents and Restricted Cash ​ ​ 87,206 ​ 87,206 ​ — ​ — ​ Total Assets Measured at Fair Value ​ $ 520,172 ​ $ 87,206 ​ $ 432,966 ​ $ — ​ The Company’s “Marketable Securities” classified as Level 2 primarily utilize broker quotes in a non-active market for valuation of these securities. No significant transfers between Level 1, Level 2 and Level 3 occurred during the year ended December 31, 2020. The Company’s policy regarding the recording of transfers between levels is to record any such transfers at the end of the reporting period.

Special Items

Special Items	12 Months Ended
	Dec. 31, 2020
Special Items
Special Items	(9) Special Items The following table summarizes the components of the Company's special items, for the year ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2020 2019 2018 Special items: ​ ​ ​ ​ ​ ​ ​ ​ ​ Parts Credit 1 ​ $ — ​ $ 18,508 ​ $ — Employee severance 2 ​ — ​ ​ 3,361 ​ — Total special items ​ $ — ​ $ 21,869 ​ $ — (1) The Company terminated an agreement with an aircraft manufacturer that obligated the Company to future aircraft lease return conditions on aircraft the Company leased. In conjunction with the terminated agreement, the aircraft manufacturer released the Company from the future aircraft lease return obligations and the Company agreed to terminate aircraft part credits previously issued by the manufacturer to the Company. As a result of the terminated agreement, the Company recorded a non-cash expense of $18.5 million (pre-tax) during 2019 to write-off the terminated aircraft part credits, which was reflected as a special items operating expense in the consolidated statement of comprehensive income. These special items are reflected in the SkyWest Airlines operating expenses under Note 3 Segment Reporting . ​ (2) During 2019, the Company incurred $3.4 million of employee severance related costs associated with the sale of ExpressJet that are also reflected in special items. These special items are reflected in the ExpressJet operating expenses under Note 3 Segment Reporting .

Capital Transactions

Capital Transactions	12 Months Ended
	Dec. 31, 2020
Capital Transactions
Capital Transactions	(10) Capital Transactions Preferred Stock The Company is authorized to issue 5,000,000 shares of preferred stock in one or more series without shareholder approval. No shares of preferred stock are presently outstanding. The Company’s Board of Directors is authorized, without any further action by the shareholders of the Company, to (i) divide the preferred stock into series; (ii) designate each such series; (iii) fix and determine dividend rights; (iv) determine the price, terms and conditions on which shares of preferred stock may be redeemed; (v) determine the amount payable to holders of preferred stock in the event of voluntary or involuntary liquidation; (vi) determine any sinking fund provisions; and (vii) establish any conversion privileges. Stock Compensation On May 7, 2019, the Company’s shareholders approved the adoption of the SkyWest, Inc. 2019 Long-Term Incentive Plan, which provides for the issuance of up to 4,500,000 shares of common stock to the Company’s directors, employees, consultants and advisors (the “2019 Incentive Plan”). The 2019 Incentive Plan provides for awards in the form of options to acquire shares of common stock, stock appreciation rights, restricted stock grants, restricted stock units and performance awards. The 2019 Incentive Plan is administered by the Compensation Committee of the Company’s Board of Directors (the “Compensation Committee”). As of December 31, 2020, the 2019 Incentive Plan had 4.1 million shares remaining available for future issuance. Stock Options The fair value of stock options awarded under the Company’s stock option plans has been estimated as of the grant date using the Black-Scholes option pricing model. The Company uses historical data to estimate option exercises and employee termination in the option pricing model. The expected term of options granted is derived from the output of the option pricing model and represents the period of time that options granted are expected to be outstanding. The expected volatilities are based on the historical volatility of the Company’s traded stock and other factors. During the years ended December 31, 2020, 2019 and 2018, the Company did not grant any options to purchase shares of common stock to its employees. Options are exercisable for a period as defined by the Compensation Committee on the date granted; however, no stock option will be exercisable before six months have elapsed from the date of grant and no stock option shall be exercisable after seven years from the date of grant. The following table summarizes the stock option activity for all of the Company’s plans for the years ended December 31, 2020, 2019 and 2018. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 ​ 2018 ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ Aggregate ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ Remaining ​ Intrinsic ​ ​ ​ Average ​ ​ ​ Average ​ ​ Number of ​ Exercise ​ Contractual ​ Value ​ Number of ​ Exercise ​ Number of ​ Exercise ​ ​ Options ​ Price ​ Term ​ ($000) ​ Options ​ Price ​ Options ​ Price Outstanding at beginning of year 60,231 ​ 14.74 3.1 years $ 3,005.1 300,580 $ 13.70 458,103 $ 13.73 ​ Granted — ​ — ​ ​ ​ ​ ​ — ​ — — ​ — ​ Exercised (2,578) ​ 14.78 ​ ​ ​ ​ ​ (232,514) ​ 13.36 (157,523) ​ 13.80 ​ Cancelled — ​ — ​ ​ ​ ​ ​ (7,835) ​ 15.86 — ​ — ​ Outstanding at end of year 57,653 ​ 14.74 2.1 years $ 1,474.5 60,231 ​ 14.74 300,580 ​ 13.70 ​ Exercisable at December 31, 2020 57,653 ​ ​ 14.74 ​ 2.1 years $ 1,474.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2019 60,231 ​ ​ 14.74 ​ 3.1 years $ 3,005.1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The total intrinsic value of options to acquire shares of the Company’s common stock that were exercised during the years ended December 31, 2020, 2019 and 2018 was $0.1 million, $10.5 million and $7.1 million, respectively. All of the Company’s stock options were vested as of December 31, 2020. The following table summarizes information about the Company’s stock options outstanding at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ Options Exercisable ​ ​ ​ ​ ​ ​ Weighted Average ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number ​ Remaining ​ Weighted Average ​ Number ​ Weighted Average Range of Exercise Prices ​ Outstanding ​ Contractual Life ​ Exercise Price ​ Exercisable ​ Exercise Price $13.00 to $13.99 2,034 0.1 years $ 13.51 ​ 2,034 $ 13.51 ​ $14.00 to $15.00 55,619 1.1 years ​ 14.78 55,619 ​ 14.78 ​ $13.00 to $15.00 57,653 1.1 years ​ $ 14.74 57,653 ​ $ 14.74 ​ ​ Restricted Stock Units During the year ended December 31, 2020, the Company granted 82,505 The following table summarizes the activity of restricted stock units granted to certain Company employees for the years ended December 31, 2020, 2019 and 2018: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ Grant-Date Fair ​ ​ Number of RSUs ​ ​ Value Non-vested RSUs outstanding at December 31, 2017 815,590 ​ $ 18.35 ​ Granted 115,044 ​ 53.40 ​ Vested (330,580) ​ 13.57 ​ Cancelled (24,273) ​ 27.77 ​ Non-vested RSUs outstanding at December 31, 2018 575,781 ​ $ 27.71 ​ Granted 104,120 ​ 48.65 ​ Vested (251,853) ​ 14.79 ​ Cancelled (143,362) ​ 30.85 ​ Non-vested RSUs outstanding at December 31, 2019 284,686 ​ $ 45.21 ​ Granted 82,505 ​ 61.45 ​ Vested (103,231) ​ 35.81 ​ Cancelled (25,983) ​ 52.31 ​ Non-vested RSUs outstanding at December 31, 2020 237,977 ​ $ 54.15 ​ ​ Performance Stock Units During the year ended December 31, 2020, the Compensation Committee granted performance share units, which are performance based restricted stock units, to certain Company employees. The PSUs are based on cumulative three-year performance-based metrics ending December 31, 2022 that the Company must meet before those awards may be measured and earned. The Company’s compensation expense for performance share units is based upon the projected number of performance share units estimated to be awarded at the conclusion of the performance period. During 2020, the Compensation Committee awarded 83,042 additional shares of stock related to the performance share grant in 2017 based on the Company’s performance for the three years ended December 31, 2019 measured against the pre-established targets for the same period. The Compensation Committee will determine the achievement of performance results and corresponding vesting of performance shares for each year’s grant in 2018, 2019 and 2020 following the conclusion of the respective performance period. At the end of each performance period, the number of shares awarded can range from 0% to 200% of the original granted amount for performance share units granted in 2020, 2019 and 2018. The following table summarizes the activity of performance share units granted at target as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ Grant-Date ​ ​ Number of PSUs ​ ​ Fair Value Non-vested PSUs outstanding at December 31, 2017 468,576 ​ $ 19.70 Granted 90,264 ​ 53.41 Additional PSUs awarded from the 2015 grant 92,335 ​ 13.62 Vested (277,029) ​ 13.62 Cancelled (3,229) ​ 30.09 Non-vested PSUs outstanding at December 31, 2018 370,917 ​ $ 30.84 Granted 87,864 ​ 48.81 Additional PSUs awarded from the 2016 grant 67,853 ​ 14.80 Vested (203,582) ​ 14.80 Cancelled (89,481) ​ 34.70 Non-vested PSUs outstanding at December 31, 2019 233,571 ​ $ 45.44 Granted 69,132 ​ 61.45 Additional PSUs awarded from the 2017 grant 83,042 ​ 35.81 Vested (166,084) ​ 35.81 Cancelled (23,052) ​ 53.66 Non-vested PSUs outstanding at December 31, 2020 196,609 ​ $ 54.17 ​ During the years ended December 31, 2020, 2019 and 2018 the Company granted fully-vested shares of common stock to the Company’s directors in the amounts of 14,643, 18,576 and 15,165 shares, respectively, with a weighted average grant-date fair value of $61.45, $48.45, and $53.40 respectively. During the year ended December 31, 2020, 2019 and 2018, the Company recorded equity-based compensation expense of $6.8 million, $10.3 million and $13.1 million, respectively. Additionally, the Company incurred $7.9 million of employee severance related costs associated with the sale of ExpressJet, partially offset by a forfeiture credit of $4.5 million, primarily resulting from stock-based compensation awards that terminated upon the sale of ExpressJet during 2019. As of December 31, 2020, the Company had $9.2 million of total unrecognized compensation cost related to non-vested restricted stock grants and non-vested performance stock units. Total unrecognized compensation cost will be adjusted for future changes in estimated forfeitures. The Company expects to recognize this cost over a weighted average period of 1.7 years. Taxes The Company’s treatment of stock option grants of non-qualified options, restricted stock units and performance shares results in the creation of a deferred tax asset, which is a temporary difference, until the time that the option is exercised or the restrictions lapse. ​ Warrants During the year ended December 31, 2020 the Company issued to Treasury warrants to purchase 370,720 shares of the Company’s common stock as part of the CARES Act payroll support. xercise price of $28.38 per share for a five-year term from the date of issuance. Additionally, the Company issued to Treasury warrants to purchase 211,416 shares of the Company’s common stock in conjunction with the Company’s $60 million borrowing under the CARES Act Secured Loan facility. warrants were issued with an e xercise price of $28.38 per share for a five-year term from the date of issuance. The weighted average fair value of these warrants was estimated at $15.22

Retirement Plans and Employee S

Retirement Plans and Employee Stock Purchase Plans	12 Months Ended
	Dec. 31, 2020
Retirement Plans and Employee Stock Purchase Plans
Retirement Plans and Employee Stock Purchase Plans	(11) Retirement Plans and Employee Stock Purchase Plans SkyWest Retirement Plan The Company sponsors the SkyWest, Inc. Employees’ Retirement Plan (the “SkyWest Plan”). Employees who are at least 18 years of age are eligible for participation in the SkyWest Plan. Employees may elect to make contributions to the SkyWest Plan. Generally, the Company matches 100% of such contributions up to levels ranging from 2% to 12 % of compensation, based on position and years of service. Additionally, a discretionary contribution may be made by the Company. The Company’s combined contributions to the SkyWest Plan were $31.9 million, $40.7 million and $35.6 million for the years ended December 31, 2020, 2019 and 2018, respectively. Employee Stock Purchase Plans In May 2009, the Company’s Board of Directors approved the SkyWest, Inc. 2009 Employee Stock Purchase Plan (the “2009 Stock Purchase Plan”). All employees who have completed 90 days of employment with the Company or one of its subsidiaries are eligible to participate in the 2009 Stock Purchase Plan, except employees who own five percent or more of the Company’s common stock. The 2009 Stock Purchase Plan enables employees to purchase shares of the Company’s common stock at a five percent discount, through payroll deductions. Employees can contribute up to 15% of their base pay, not to exceed $25,000 each calendar year, for the purchase of shares. Shares are purchased semi-annually at a five percent discount based on the end of the period price. Employees can terminate their participation in the 2009 Stock Purchase Plan at any time upon written notice. The following table summarizes purchases made under the 2009 Employee Stock Purchase Plans during the years ended December 31, 2020, 2019 and 2018: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Number of shares purchased ​ 65,512 ​ 65,148 ​ 60,950 ​ Average price of shares purchased ​ $ 42.45 ​ $ 48.58 ​ $ 49.85 ​ The 2009 Stock Purchase Plan is a non-compensatory plan under the accounting guidance. Therefore, no compensation expense was recorded for the years ended December 31, 2020, 2019 and 2018.

Stock Repurchase

Stock Repurchase	12 Months Ended
	Dec. 31, 2020
Stock Repurchase
Stock Repurchase	(12) Stock Repurchase The Company’s Board of Directors has adopted a stock repurchase program which authorizes the Company to repurchase shares of the Company’s common stock in the public market or in private transactions, from time to time, at prevailing prices. The Company’s stock repurchase program authorizes the repurchase of up to $250.0 million of the Company’s common stock commencing on February 5, 2019, of which $139.6 million remained available at December 31, 2020. Under the terms of the Treasury Loan Agreement, the Company is restricted from repurchasing shares of its common stock for a twelve-month period following repayment of the loan in full. During the years ended December 31, 2020, 2019 and 2018, the Company repurchased 0.4 million, 1.7 million and 1.0 million shares of common stock for approximately $20.0 million, $94.6 million and $54.4 million, respectively at a weighted average price per share of $51.87, $56.86 and $56.25, respectively. Additionally, during the year ended December 31, 2020, 2019 and 2018, the Company paid $6.2 million, $9.3 million and $13.6 million, respectively, for a net settlement of the income tax obligation on employee equity awards that vested during the applicable periods.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2020
Related-Party Transactions
Related-Party Transactions	(13) Related-Party Transactions During the year ended December 31, 2020, the Company purchased $223,050 of spare aircraft parts from an entity affiliated with a director of the Company.

Gain on Sale of ExpressJet

Gain on Sale of ExpressJet	12 Months Ended
	Dec. 31, 2020
Gain on Sale of ExpressJet
Gain on Sale of ExpressJet	(14) Gain on Sale of ExpressJet On January 22, 2019, the Company completed the sale of its former wholly owned subsidiary ExpressJet. The Company recorded a gain of $46.5 million (pre-tax) from the sale of ExpressJet. The closing of the transaction was completed in two parts, through an asset sale and stock sale, as further described below. ​ Asset Sale ​ On January 11, 2019, pursuant to the terms and conditions of the Asset Purchase Agreement, dated as of December 17, 2018, by and among the Company, ExpressJet and United, United acquired certain specified assets and liabilities of ExpressJet, including, among other things, aircraft engines, auxiliary power units, rotable spare parts, ground support equipment and flight training equipment for $60.8 million in cash, subject to certain purchase price adjustments (the “Asset Sale”). Certain assets and liabilities of ExpressJet were expressly excluded from the Asset Sale. ​ Stock Sale ​ Additionally, on January 22, 2019, pursuant to the terms and conditions of the Stock Purchase Agreement, dated as of December 17, 2018, by and among the Company and ManaAir, LLC, a company in which United owns a minority interest (the “Buyer”), the Buyer acquired all of the outstanding shares of capital stock of ExpressJet from the Company for $18.8 million in cash, subject to certain purchase price adjustments (the “Stock Sale,”). To facilitate payment of the purchase price for the Stock Sale, at the closing of the Stock Sale, the Company loaned $26 million to Kair Enterprises, Inc. (the “Borrower”), the majority owner of the Buyer. Such loan accrues interest at the rate of 6.85% per annum, matures on the last business day of the last month immediately preceding the two-year anniversary of the closing of the Stock Sale and is secured by, among other things, the Borrower’s ownership interests in the Buyer. The Company evaluated the collectability of this loan balance as of December 31, 2020 under Topic 326. See Note 1 - Flying Agreements and Airport Customer Services and Other Revenues Allowance for Credit Losses

Investment in Other Companies

Investment in Other Companies	12 Months Ended
	Dec. 31, 2020
Investment in Other Companies
Investment in Other Companies	(15) Investment in Other Companies During 2019, the Company created a joint venture with Regional One, Inc. (“Regional One”) by investing $22.3 million for a 75% ownership interest in Aero Engines, LLC. (“Aero Engines”). The primary purpose of Aero Engines is to lease engines to third parties. Aero Engines requires unanimous approval from the Company and Regional One for its engine purchases, dispositions, lease agreements with third parties and all other material transactions. The Company determined Aero Engines is a variable interest entity as the Company has a 75% ownership interest in Aero Engines and all material decisions require unanimous approval from the Company and Regional One, resulting in disproportionate ownership rights relative to voting rights. As unanimous approval is required for all Aero Engines’ material activities. Aero Engines has no primary beneficiary. The Company accounts for its investment in Aero Engines under the equity method. The Company’s exposure in its investment in Aero Engines primarily consists of the Company’s portion of income or loss from Aero Engines’ engine lease agreements with third parties and the Company’s ownership percentage in Aero Engines’ engines book value. The Company purchased 15 spare engines and sold the 15 spare engines to Aero Engines at net book value during 2019. Since the initial investment, the Company has invested an additional $1.0 million into Aero Engines during 2020. Aero Engines had no debt outstanding as of December 31, 2020. As of December 31, 2020, the Company’s investment balance in Aero Engines was $25.5 million. The Company’s investment in Aero Engines has been recorded in “Other Assets” on the Company’s consolidated balance sheet. The Company’s portion of the income generated by Aero Engines for 2020 was $1.6 million.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events
Subsequent Events	(16) Subsequent Events On January 15, 2021, SkyWest Airlines entered into a Payroll Support Program Extension Agreement (the “PSP Extension Agreement”) with Treasury with respect to a payroll grant program under the Consolidated Appropriations Act, 2021 (“2021 Appropriations Act”). ​ Payroll Support Program Extension Agreement ​ Pursuant to the PSP Extension Agreement, SkyWest Airlines expects to receive from Treasury approximately $233.1 million in the aggregate during the first quarter of 2021. ​ In connection with the receipt of financial assistance under the PSP Extension Agreement, SkyWest Airlines is required to comply with the relevant provisions of the 2021 Appropriations Act, many of which are substantially similar to the requirements placed on SkyWest Airlines by the Payroll Support Program under the CARES Act. The relevant provisions include the requirement that the funding be used exclusively for the continuation of payment of employee wages, salaries and benefits. Similar to the Payroll Support Program under the CARES Act, SkyWest Airlines and, in some cases, the Company will also be subject to certain restrictions, including, but not limited to, limitations on involuntary terminations, salary reductions and furloughs through March 31, 2021, restrictions on the payment of dividends and the repurchase of shares through October 1, 2022, and certain limitations on executive compensation. SkyWest Airlines is also required to recall employees involuntarily terminated or furloughed after September 30, 2020 with pay from December 1, 2020 to March 31, 2021. ​ Promissory Note ​ As partial compensation to Treasury for the provision of financial assistance under the PSP Extension Agreement, SkyWest Airlines issued, and the Company guaranteed, a promissory note (the “Promissory Note”) to Treasury on the Closing Date. The Promissory Note provides for SkyWest Airlines’ unconditional promise to pay to Treasury the expected principal sum of up to approximately $39.9 million. ​ The Promissory Note will bear interest at a rate equal to 1.00% per annum until the fifth anniversary of the Closing Date, and 2.00% plus an interest rate based on the secured overnight financing rate per annum (but not less than 0.00%) thereafter until the tenth anniversary of the Closing Date (the “Maturity Date”). Accrued interest will be payable in arrears on the last business day of each of March and September of each year, beginning with March 31, 2021. The aggregate unpaid principal amount of the Promissory Note, all accrued and unpaid interest and all other amounts payable under the Promissory Note will be due and payable on the Maturity Date. ​ Warrant Agreement and Warrants ​ In connection with the PSP Extension Agreement and as partial compensation to Treasury for the provision of financial assistance under the PSP Extension Agreement, the Company will issue warrants (each a “Warrant” and, collectively, the “Warrants”) to Treasury to purchase up to an expected aggregate of 98,815 shares (the “Warrant Shares”) of the Company’s common stock, at an exercise price of $40.41 per share, which was the closing price of the Common Stock on The Nasdaq Stock Market on December 24, 2020. The Warrants will be issued pursuant to the terms of a Warrant Agreement entered into by the Company and Treasury on January 15, 2021. The number of Warrant Shares to be issued is subject to adjustment as a result of certain anti-dilution provisions contained in the Warrants. ​ Treasury Loan Agreement Borrowing Extension ​ On January 15, 2021, SkyWest Airlines and the Company entered into an additional amendment to the Loan Agreement with Treasury to provide that the deadline pursuant to which SkyWest Airlines may, at its discretion, borrow additional amounts under the facility was extended from March 26, 2021 to May 28, 2021. The other terms of the Loan Agreement were not affected.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data (Unaudited)
Quarterly Financial Data (Unaudited)	(17) Quarterly Financial Data (Unaudited) Unaudited summarized financial data by quarter for 2020 and 2019 is as follows (in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2020 ​ ​ First ​ Second ​ Third ​ Fourth ​ ​ ​ ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year Operating revenues $ 729,936 $ 350,039 $ 457,493 $ 589,638 $ 2,127,106 ​ Operating income ​ 66,321 ​ (4,403) ​ 74,553 ​ (27,669) ​ 108,802 ​ Net income ​ 29,988 ​ (25,715) ​ 33,662 ​ (46,450) ​ (8,515) ​ Net income per common share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ 0.60 ​ (0.51) ​ 0.67 ​ (0.93) ​ (0.17) ​ Diluted ​ 0.59 ​ (0.51) ​ 0.66 ​ (0.93) ​ (0.17) ​ Weighted average common shares: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic: ​ 50,277 ​ 50,140 ​ 50,181 ​ 50,181 ​ 50,195 ​ Diluted: ​ 50,559 ​ 50,140 ​ 50,622 ​ 50,181 ​ 50,195 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2019 ​ ​ First ​ Second ​ Third ​ Fourth ​ ​ ​ ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year Operating revenues $ 723,694 $ 744,383 $ 760,295 $ 743,591 $ 2,971,963 ​ Operating income ​ 96,419 ​ 144,093 ​ 146,441 ​ 125,305 ​ ​ 512,258 ​ Net income (1) ​ 88,181 ​ 88,052 ​ 91,339 ​ 72,527 ​ ​ 340,099 ​ Net income per common share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ 1.71 ​ 1.72 ​ 1.80 ​ 1.44 ​ ​ 6.68 ​ Diluted ​ 1.69 ​ 1.71 ​ 1.79 ​ 1.43 ​ ​ 6.62 ​ Weighted average common shares: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic: ​ 51,440 ​ 51,145 ​ 50,746 ​ 50,395 ​ ​ 50,932 ​ Diluted: ​ 52,098 ​ 51,477 ​ 51,129 ​ 50,796 ​ ​ 51,375 ​ ​ (1) Net income for the first quarter of 2019 included a $46.5 million gain related to the sale of ExpressJet (see Note 14 Gain on Sale of ExpressJet for more details) and a $21.9 million special charge (see Note 9 Special Items for more details).

SCHEDULE II-VALUATION AND QUALI

SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2020
SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS
SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS	SKYWEST, INC. AND SUBSIDIARIES SCHEDULE II—VALUATION AND QUALIFYING ACCOUNTS For the Years Ended December 31, 2020, 2019 and 2018 (Dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Additions ​ ​ ​ ​ ​ Balance at ​ Charged to ​ ​ ​ ​ ​ ​ ​ Beginning ​ Costs and ​ ​ ​ Balance at Description ​ of Year ​ Expenses ​ Deductions ​ End of Year Year ended December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for inventory obsolescence ​ $ 15,890 ​ 3,786 — $ 19,676 ​ Allowance for doubtful accounts receivable ​ ​ 18 ​ ​ — ​ (18) ​ ​ — ​ Allowance for credit losses (adoption of Topic 326) ​ ​ 15,388 ​ 30,837 — ​ 46,225 ​ ​ ​ $ 31,296 ​ 34,623 (18) $ 65,901 ​ Year ended December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for inventory obsolescence ​ $ 22,141 ​ — (6,251) $ 15,890 ​ Allowance for doubtful accounts receivable ​ ​ 158 ​ — (140) ​ 18 ​ ​ ​ $ 22,299 ​ — (6,391) $ 15,908 ​ Year ended December 31, 2018: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for inventory obsolescence ​ $ 17,098 ​ 5,043 — $ 22,141 ​ Allowance for doubtful accounts receivable ​ ​ 157 ​ 1 — ​ 158 ​ ​ ​ $ 17,255 ​ 5,044 — ​ $ 22,299 ​ ​

Nature of Operations and Summ_2

Nature of Operations and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Nature of Operations and Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The Company’s consolidated financial statements include the accounts of the Company and the SkyWest Airlines, ExpressJet (for the periods owned by the Company) and SkyWest Leasing segments, with all inter-company transactions and balances having been eliminated. In preparing the accompanying consolidated financial statements, the Company has reviewed, as determined necessary by the Company’s management, events that have occurred after December 31, 2020, through the filing date of the Company’s annual report with the U.S. Securities and Exchange Commission.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less to be cash equivalents. The Company had no restricted cash as of December 31, 2020 and 2019.
Marketable securities	Marketable Securities The Company’s investments in debt securities are classified as available-for-sale and are reported at fair market value with the net unrealized appreciation reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. At the time of sale, any realized appreciation or depreciation, calculated by the specific identification method, is recognized in other income and expense. At December 31, 2020 and 2019, the fair market value of the available-for-sale securities was the amortized cost. The Company’s position in marketable securities as of December 31, 2020 and 2019 was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross unrealized ​ Gross unrealized ​ ​ ​ ​ At December 31, 2020 Amortized Cost holding gains holding losses Fair market value Total cash and cash equivalents ​ $ 215,723 ​ $ — ​ $ — ​ $ 215,723 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bond and bond funds ​ $ 117,928 ​ $ — ​ $ — ​ $ 117,928 ​ Commercial Paper ​ 492,257 ​ — ​ — ​ 492,257 ​ Total marketable securities ​ $ 610,185 ​ $ — ​ $ — ​ $ 610,185 ​ Total assets measured at fair value ​ $ 825,908 ​ $ — ​ $ — ​ $ 825,908 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross unrealized ​ ​ Gross unrealized ​ ​ ​ ​ At December 31, 2019 Amortized Cost holding gains holding losses Fair market value Total cash and cash equivalents ​ $ 87,206 ​ $ — ​ $ — ​ $ 87,206 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bond and bond funds ​ $ 267,243 ​ $ — ​ $ — ​ $ 267,243 ​ Commercial Paper ​ 165,723 ​ — ​ — ​ 165,723 ​ Total marketable securities ​ $ 432,966 ​ $ — ​ $ — ​ $ 432,966 ​ Total assets measured at fair value ​ $ 520,172 ​ $ — ​ $ — ​ $ 520,172 ​ ​
Inventories	Inventories Inventories include expendable parts, fuel and supplies and are valued at cost (FIFO basis) less an allowance for obsolescence based on historical results, excess parts and management’s expectations of future operations. Expendable inventory parts are charged to expense as used. An obsolescence allowance for flight equipment expendable parts is accrued based on estimated lives of the corresponding fleet types and salvage values. The inventory allowance as of December 31, 2020 and 2019 was $19.7 million and $15.9 million, respectively.
Property and Equipment	Property and Equipment Property and equipment are stated at cost and depreciated over their useful lives to their estimated residual values using the straight-line method as follows: ​ ​ ​ Assets ​ Depreciable Life ​ Current Residual Value ​ Aircraft, rotable spares, and spare engines ​ up to 22 years up to 20 % ​ Ground equipment ​ up to 10 years 0 % ​ Office equipment ​ up to 7 years ​ 0 % ​ Leasehold improvements ​ Shorter of 15 years or lease term 0 % ​ Buildings ​ 20 - 39.5 years 0 % ​
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets As of December 31, 2020, the Company had approximately $5.4 billion of property and equipment and related assets. In accounting for these long-lived and intangible assets, the Company makes estimates about the expected useful lives of the assets, the expected residual values of certain of these assets, and the potential for impairment based on the fair value of the assets and the cash flows they generate. Factors indicating potential impairment include, but are not limited to, significant decreases in the market value of the long-lived assets, a significant change in the condition of the long-lived assets and operating cash flow losses associated with the use of the long-lived assets. On a periodic basis, the Company evaluates whether impairment indicators are present. When considering whether or not impairment of long- lived assets exists, the Company groups similar assets together at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities and compare the undiscounted cash flows for each asset group to the net carrying amount of the assets supporting the asset group. Asset groupings are done at the fleet or contract level. The Company did not recognize any impairment charges of long-lived assets during the years ended December 31, 2020, 2019 and 2018.
Capitalized Interest	Capitalized Interest Interest is capitalized on aircraft purchase deposits as a portion of the cost of the asset and is depreciated over the estimated useful life of the asset. During the years ended December 31, 2020, 2019 and 2018, the Company capitalized interest costs of approximately $1.7 million, $1.6 million, and $1.5 million, respectively.
Maintenance	Maintenance The Company operates under a U.S. Federal Aviation Administration approved continuous inspection and maintenance program. The Company uses the direct expense method of accounting for its regional jet engine overhauls wherein the expense is recorded when the overhaul event occurs. The Company has engine services agreements with third-party vendors to provide long-term engine services covering the scheduled and unscheduled repairs for most of its aircraft. Under the terms of the agreements, the Company pays a fixed dollar amount per engine hour flown on a monthly basis and the third-party vendors will assume the responsibility to repair the engines at no additional cost to the Company, subject to certain specified exclusions. Maintenance costs under these contracts are recognized when the engine hour is flown pursuant to the terms of each contract. The costs of maintenance for airframe and avionics components, landing gear and other recurring maintenance are expensed as incurred. During the year ended December 31, 2020, the Company wrote-off $3.7 million of long-lived maintenance assets at maintenance locations the Company vacated during the year.
Flying Agreements and Airport Customer Service and Other Revenues	Flying Agreements and Airport Customer Service and Other Revenues The Company recognizes flying agreements revenue and airport customer service and other revenues when the service is provided under its code-share agreements. Under the Company’s fixed-fee arrangements (referred to as “capacity purchase agreements”, “fixed-fee arrangements,” or “fixed-fee contracts”) with Delta, United, American and Alaska (each, a “major airline partner”), the major airline partner generally pays the Company a fixed-fee for each departure, flight hour (measured from takeoff to landing, excluding taxi time) or block hour (measured from takeoff to landing, including taxi time) incurred, and an amount per aircraft in service each month with additional incentives based on flight completion and on-time performance. The major airline partner also directly pays for or reimburses the Company for certain direct expenses incurred under the capacity purchase arrangement, such as fuel, airport landing fees and airport rents. Under the capacity purchase arrangements, the Company’s performance obligation is met and revenue is recognized when each flight is completed, measured in completed block hours, and is reflected in flying agreements revenue. The transaction price for the capacity purchase agreements is determined from the fixed-fee consideration, incentive consideration and directly reimbursed expenses earned as flights are completed over the agreement term. For the year ended December 31, 2020, capacity purchase arrangements represented approximately Under the Company’s prorate arrangements (referred to as a “prorate” or “revenue-sharing” arrangement), the major airline partner and the Company negotiate a passenger fare proration formula, pursuant to which the Company receives a percentage of the ticket revenues for those passengers traveling for one portion of their trip on a Company airline and the other portion of their trip on the major airline partner. Under the Company’s prorate flying agreements, the performance obligation is met and revenue is recognized when each flight is completed based upon the portion of the prorate passenger fare the Company anticipates that it will receive for each completed flight. The transaction price for the prorate agreements is determined from the proration formula derived from each passenger ticket amount on each completed flight over the agreement term. For the year ended December 31, 2020, prorate flying arrangements represented approximately Lease, airport services and other revenues primarily consist of ground handling functions, such as gate and ramp agent services at applicable airports where the Company provides such services. The transaction price for airport customer service agreements is determined from an agreed-upon rate by location applied to the applicable number of flights handled by the Company over the agreement term. Additionally, airport customer service and other revenues includes revenue generated from aircraft and spare engines leased to third parties. Of the Company’s $5.4 billion of property and equipment, net as of December 31, 2020, $271.1 million of regional jet aircraft and spare engines were leased to third parties under operating leases. The Company mitigates the residual asset risks of these assets by leasing aircraft and engine types that can be operated by the Company in the event of a default. A portion of the Company’s leases to third parties contain variable payments from lessees based on departures where the Company pays for maintenance. Additionally, the operating leases typically have specified lease return condition requirements paid by the lessee to the Company and the Company typically maintains inspection rights under the leases. ​ The following table represents the Company’s flying agreements revenue by type for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 2018 Capacity purchase agreements revenue: flight operations ​ $ 945,008 ​ $ 1,538,062 ​ $ 1,856,253 Capacity purchase agreements revenue: aircraft lease ​ 846,933 ​ 830,247 ​ 814,518 Prorate agreements revenue ​ 268,860 ​ 520,956 ​ 498,749 Flying agreements revenue ​ $ 2,060,801 ​ $ 2,889,265 ​ $ 3,169,520 ​ A portion of the Company’s compensation under its capacity purchase agreements is designed to reimburse the Company for certain aircraft ownership costs. The consideration for aircraft ownership costs varies by agreement but is intended to cover either the Company’s aircraft principal and interest debt service costs, its aircraft depreciation and interest expense or its aircraft lease expense costs while the aircraft is under contract. The consideration received for the use of the aircraft under the Company’s capacity purchase agreements is reflected as lease revenue, inasmuch as the agreements identify the “right of use” of a specific type and number of aircraft over a stated period of time. The lease revenue associated with the Company’s capacity purchase agreements is accounted for as an operating lease and is reflected as flying agreements revenue on the Company’s consolidated statements of comprehensive income. The Company has not separately stated aircraft rental income and aircraft rental expense in the consolidated statement of comprehensive income since the use of the aircraft is not a separate activity of the total service provided. Under the Company’s capacity purchase agreements, the Company is paid a fixed amount per month per aircraft over the contract term. The Company recognizes revenue attributed to the Fixed Monthly Payments proportionate to the number of block hours complete during each reporting period, relative to the estimated number of block hours we anticipate completing over the remaining contract term. Due to the material decrease in completed block hours in 2020 from historical levels and from anticipated future levels over the remaining contract terms, the Company determined the amount of Fixed Monthly Payments received in 2020 was disproportionately high relative to the number of block hours completed during 2020. The Company anticipates the future number of block hours it will complete over the remaining capacity purchase agreements will significantly increase from 2020 levels. Accordingly, the Company deferred recognizing revenue of $110.7 million of fixed monthly cash payments the Company received under its capacity purchase agreements during 2020. The Company’s deferred revenue related to the fixed payments will adjust over the remaining contract term for each capacity purchase agreement based on the number of block hours it completes each reporting period relative to the number of block hours it anticipates completing over the remaining contract term of each capacity purchase agreement. ​ In the event a flying agreement includes a mid-term rate reset to adjust rates prospectively and the contractual rates under the Company’s flying agreements have not been finalized at quarterly or annual financial statement dates, the Company applies the variable constraint guidance under Topic 606, where the Company records revenue to the extent it believes that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. ​ In several of the Company’s agreements, the Company is eligible to receive incentive compensation upon the achievement of certain performance criteria. The incentives are defined in the agreements and are measured and determined on a monthly, quarterly or semi-annual basis. At the end of each period during the term of an agreement, the Company calculates the incentives achieved during that period and recognizes revenue attributable to that agreement accordingly, subject to the variable constraint guidance under Topic 606. The following summarizes the significant provisions of each code-share agreement the Company has with each major airline partner through SkyWest Airlines: Delta Connection Agreements Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates Delta Connection Agreement (capacity purchase arrangement) ​ ● E175 ● CRJ 900 ● CRJ 700 ​ 71 39 6 ​ ● Individual aircraft have scheduled removal dates from 2021 to 2030 ● ​ Delta Connection Prorate Agreement (prorate arrangement) ​ ● CRJ 200 ​ 26 ​ ● Terminable with 30-day ​ ​ United Express Agreements ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates United Express Agreements (capacity purchase arrangement) ​ ● E175 ● CRJ 700 ● CRJ 200 ​ 90 19 70 ​ ​ ● Individual aircraft have scheduled removal dates under the agreement between 2022 and 2029 ● ​ United Express Prorate Agreement (prorate arrangement) ​ ● CRJ 200 ​ ​ 34 ​ ● Terminable with 120-day ​ ​ American Capacity Purchase Agreement ​ ​ ​ ​ ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates American Agreement (capacity purchase arrangement) ​ ● CRJ 700 ​ ​ 65 ​ ● ● ​ ​ Alaska Capacity Purchase Agreement ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates Alaska Agreement (capacity purchase arrangement) ​ ● E175 ​ ​ 32 ​ ● ● ​ ​ In addition to the contractual arrangements described above, as of December 31, 2020, SkyWest Airlines entered into a capacity purchase agreement with American to place 20 E175 aircraft into service. The delivery dates for the 20 new E175 aircraft are currently scheduled for 2021 and 2022 and the aircraft are expected to be placed into service in 2022. SkyWest Airlines also entered into an agreement with American to place 25 used CRJ700s under a multi-year capacity purchase agreement beginning in 2021. Final delivery dates may be adjusted based on various factors. ​ SkyWest Airlines also entered into an agreement with Delta to place one CRJ900 aircraft under a capacity purchase agreement in 2021. The Company anticipates Delta will acquire the aircraft and SkyWest operate the aircraft. ​ When an aircraft is scheduled to be removed from a capacity purchase arrangement, the Company may, as practical under the circumstances, negotiate an extension with the respective major airline partner, negotiate the placement of the aircraft with another major airline partner, return the aircraft to the lessor if the aircraft is leased and the lease is expiring, place owned aircraft for sale, or pursue other uses for the aircraft. Other uses for the aircraft may include placing the aircraft in a prorate arrangement, leasing the aircraft to a third party or parting out the aircraft to use the engines and parts as spare inventory or to lease the engines to a third party. ​ The following table represents the Company’s lease, airport services and other revenues for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 2018 Airport customer service and other revenue ​ $ 25,804 ​ $ 45,538 ​ $ 48,236 Operating lease income relating to lease payments ​ 34,791 ​ 27,552 ​ 3,923 Operating lease income relating to variable lease payments ​ 5,710 ​ 9,608 ​ — Lease, airport services and other ​ $ 66,305 ​ $ 82,698 ​ $ 52,159 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 $ 43,573 2022 ​ 43,390 ​ 2023 ​ 42,837 ​ 2024 ​ 42,530 ​ 2025 ​ 39,082 ​ Thereafter ​ 155,089 ​ ​ ​ $ 366,501 ​ ​ The Company’s operating revenues could be impacted by a number of factors, including changes to the Company’s code-share agreements with its major airline partners, changes in flight schedules, contract modifications resulting from contract renegotiations, the Company’s ability to earn incentive payments contemplated under the Company’s code-share agreements and settlement of reimbursement disputes with the Company’s major airline partners. ​ Other ancillary revenues commonly associated with airlines, such as baggage fee revenue, ticket change fee revenue and the marketing component of the sale of mileage credits, are retained by the Company’s major airline partners on flights that the Company operates under its code-share agreements. ​ As of December 31, 2020, the Company had $34.5 million in accounts receivable of which $27.5 million related to flying agreements. As of December 31, 2019, the Company had $83.0 million in accounts receivable of which $58.8 million related to flying agreements.
Allowance for Credit Losses	Allowance for Credit Losses The Company monitors publicly available credit ratings for entities for which the Company has a significant receivable balance. As of December 31, 2020, the Company had gross receivables of $56.1 million in current assets and gross receivables of $157.4 million in other long-term assets. The Company has established credit loss reserves based on publicly available historic default rates issued by a third party for companies with similar credit ratings, factoring in the term of the respective accounts receivable or note receivable. During the twelve months ended December 31, 2020, the collectability on a note receivable from Kair Enterprises, Inc. associated with the Company’s sale of ExpressJet in 2019 became uncertain due to ExpressJet ceasing operations during the year and the credit ratings were lowered on certain entities for which the Company has outstanding accounts receivable or notes receivable, which were the primary drivers for the increase in the Company’s credit loss reserve when benchmarked against historic default rates as of January 1, 2020, when the Company adopted Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments” (“Topic 326”) . The following table summarizes the changes in allowance for credit losses: ​ ​ ​ ​ ​ Allowance for Credit Losses Balance at January 1, 2020 ​ $ 15,388 Additions to credit loss reserves ​ 30,837 Write-offs charged against allowance ​ — Balance at December 31, 2020 ​ $ 46,225
Income Taxes	Income Taxes The Company recognizes a net liability or asset for the deferred tax consequences of all temporary differences between the tax basis of assets and liabilities and their reported amounts in the consolidated financial statements that are expected to result in taxable or deductible amounts in future years when the reported amounts of the assets and liabilities are recovered or settled.
Net Income (Loss) Per Common Share	Net Income (Loss) Per Common Share Basic net income (loss) per common share (“Basic EPS”) excludes dilution and is computed by dividing net income by the weighted average number of common shares outstanding during the period. Diluted net income per common share (“Diluted EPS”) reflects the potential dilution that could occur if stock options or other contracts to issue common stock were exercised or converted into common stock. The computation of Diluted EPS does not assume exercise or conversion of securities that would have an anti-dilutive effect on net income (loss) per common share. During the year ended December 31, 2020, 1,074,375 shares reserved for the issuance of employee equity awards and warrants to acquire the Company’s common stock were excluded in the computation of Diluted EPS since the Company reported a net loss for the year ended December 31, 2020. During the year ended December 31, 2019, 150,000 performance share units (at target performance) were excluded in the computation of Diluted EPS since the Company had not achieved the minimum target thresholds as of December 31, 2019. During the year ended December 31, 2018, 207,000 performance share units (at target performance) were excluded in the computation of Diluted EPS since the Company had not achieved the minimum target thresholds as of December 31, 2018. The calculation of the weighted average number of common shares outstanding for Basic EPS and Diluted EPS are as follows for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Numerator: ​ ​ ​ ​ Net income (loss) ​ $ (8,515) ​ $ 340,099 ​ $ 280,372 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic earnings per share weighted average shares ​ 50,195 ​ 50,932 ​ 51,914 ​ Dilution due to stock options and restricted stock units ​ — ​ 443 ​ 957 ​ Diluted earnings per share weighted average shares ​ 50,195 ​ 51,375 ​ 52,871 ​ Basic earnings (loss) per share ​ $ (0.17) ​ $ 6.68 ​ $ 5.40 ​ Diluted earnings (loss) per share ​ $ (0.17) ​ $ 6.62 ​ $ 5.30 ​
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) includes charges and credits to stockholders’ equity that are not the result of transactions with the Company’s shareholders, including changes in unrealized appreciation on marketable debt securities.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts reported in the consolidated balance sheets for receivables and accounts payable approximate fair values because of the immediate or short-term maturity of these financial instruments. Marketable securities are reported at fair value based on market quoted prices in the consolidated balance sheets. If quoted prices in active markets are no longer available, the Company has estimated the fair values of these securities utilizing a discounted cash flow analysis. These analyses consider, among other items, the collateralization underlying the security investments, the creditworthiness of the counterparty, the timing of expected future cash flows, and the expectation of the next time the security is expected to have a successful auction. The fair value of the Company’s long-term debt is estimated based on current rates offered to the Company for similar debt and was approximately $3,244.0 million as of December 31, 2020, as compared to the carrying amount of $3,236.0 million as of December 31, 2020. The Company’s fair value of long-term debt as of December 31, 2019 was $3,049.1 million as compared to the carrying amount of $3,017.5 million as of December 31, 2019.
Segment Reporting	Segment Reporting Generally accepted accounting principles require disclosures related to components of a company for which separate financial information is available to, and regularly evaluated by, the Company’s chief operating decision maker when deciding how to allocate resources and in assessing performance. The Company’s three operating segments (prior to the sale of ExpressJet in January 2019) consist of the operations conducted by SkyWest Airlines, ExpressJet (for the periods owned by the Company) and SkyWest Leasing. Following the sale of ExpressJet, the Company has two reportable segments: SkyWest Airlines and SkyWest Leasing. Information pertaining to the Company’s reportable segments is presented in Note 3, Segment Reporting
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Standards In June 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments” (“Topic 326”), which requires measurement and recognition of expected credit losses for financial assets held and requires enhanced disclosure regarding significant estimates and judgments used in estimating credit losses. Topic 326 is effective for the Company beginning January 1, 2020. The Company adopted Topic 326 on January 1, 2020. The Company’s primary financial assets as of December 31, 2019 included trade receivables from its flying agreements, a note receivable from the sale of ExpressJet, and receivables from aircraft manufacturers and other third parties in the airline industry. The Company recorded a credit loss of

Nature of Operations and Summ_3

Nature of Operations and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of number of aircraft held by entity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CRJ200 CRJ700 CRJ900 E175 Total Delta 26 ​ 6 ​ 39 ​ 71 ​ 142 ​ United 104 ​ 19 ​ — ​ 90 ​ 213 ​ American — ​ 65 ​ — ​ — ​ 65 ​ Alaska — ​ — ​ — ​ 32 ​ 32 ​ Aircraft in scheduled service ​ 130 ​ 90 ​ 39 ​ 193 ​ 452 ​ Leased to third parties 2 ​ 34 ​ 5 ​ — ​ 41 ​ Other* 74 ​ 30 ​ 4 ​ — ​ 108 ​ Total Fleet 206 ​ 154 ​ 48 ​ 193 ​ 601 ​ *As of December 31, 2020, these aircraft have been removed from service and are in the process of being placed under a leasing arrangement with a third party, are aircraft transitioning between code-share agreements with the Company’s major airline partners and being used as a supplemental spare aircraft, or are in the process of being parted out.
Schedule of marketable securities	At December 31, 2020 and 2019, the fair market value of the available-for-sale securities was the amortized cost. The Company’s position in marketable securities as of December 31, 2020 and 2019 was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross unrealized ​ Gross unrealized ​ ​ ​ ​ At December 31, 2020 Amortized Cost holding gains holding losses Fair market value Total cash and cash equivalents ​ $ 215,723 ​ $ — ​ $ — ​ $ 215,723 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bond and bond funds ​ $ 117,928 ​ $ — ​ $ — ​ $ 117,928 ​ Commercial Paper ​ 492,257 ​ — ​ — ​ 492,257 ​ Total marketable securities ​ $ 610,185 ​ $ — ​ $ — ​ $ 610,185 ​ Total assets measured at fair value ​ $ 825,908 ​ $ — ​ $ — ​ $ 825,908 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross unrealized ​ ​ Gross unrealized ​ ​ ​ ​ At December 31, 2019 Amortized Cost holding gains holding losses Fair market value Total cash and cash equivalents ​ $ 87,206 ​ $ — ​ $ — ​ $ 87,206 ​ Marketable securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bond and bond funds ​ $ 267,243 ​ $ — ​ $ — ​ $ 267,243 ​ Commercial Paper ​ 165,723 ​ — ​ — ​ 165,723 ​ Total marketable securities ​ $ 432,966 ​ $ — ​ $ — ​ $ 432,966 ​ Total assets measured at fair value ​ $ 520,172 ​ $ — ​ $ — ​ $ 520,172 ​ ​
Schedule of property and equipment	​ ​ Assets ​ Depreciable Life ​ Current Residual Value ​ Aircraft, rotable spares, and spare engines ​ up to 22 years up to 20 % ​ Ground equipment ​ up to 10 years 0 % ​ Office equipment ​ up to 7 years ​ 0 % ​ Leasehold improvements ​ Shorter of 15 years or lease term 0 % ​ Buildings ​ 20 - 39.5 years 0 % ​
Schedule of future minimum rental payments for operating leases	The following table summarizes future minimum rental payments primarily related to leased aircraft required under operating leases that had initial or remaining non-cancelable lease terms as of December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ 2021 $ 85,869 2022 ​ 77,780 ​ 2023 ​ 69,530 ​ 2024 ​ 28,091 ​ 2025 ​ 15,751 ​ Thereafter ​ 82,719 ​ ​ ​ $ 359,740 ​
Schedule of allowance for credit losses	The following table summarizes the changes in allowance for credit losses: ​ ​ ​ ​ ​ Allowance for Credit Losses Balance at January 1, 2020 ​ $ 15,388 Additions to credit loss reserves ​ 30,837 Write-offs charged against allowance ​ — Balance at December 31, 2020 ​ $ 46,225
Schedule of net income (loss) per common share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Numerator: ​ ​ ​ ​ Net income (loss) ​ $ (8,515) ​ $ 340,099 ​ $ 280,372 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic earnings per share weighted average shares ​ 50,195 ​ 50,932 ​ 51,914 ​ Dilution due to stock options and restricted stock units ​ — ​ 443 ​ 957 ​ Diluted earnings per share weighted average shares ​ 50,195 ​ 51,375 ​ 52,871 ​ Basic earnings (loss) per share ​ $ (0.17) ​ $ 6.68 ​ $ 5.40 ​ Diluted earnings (loss) per share ​ $ (0.17) ​ $ 6.62 ​ $ 5.30 ​
Flying agreements
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of revenue by type	The following table represents the Company’s flying agreements revenue by type for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 2018 Capacity purchase agreements revenue: flight operations ​ $ 945,008 ​ $ 1,538,062 ​ $ 1,856,253 Capacity purchase agreements revenue: aircraft lease ​ 846,933 ​ 830,247 ​ 814,518 Prorate agreements revenue ​ 268,860 ​ 520,956 ​ 498,749 Flying agreements revenue ​ $ 2,060,801 ​ $ 2,889,265 ​ $ 3,169,520
Airport customer service and other revenue
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of revenue by type	​ The following table represents the Company’s lease, airport services and other revenues for the years ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 2018 Airport customer service and other revenue ​ $ 25,804 ​ $ 45,538 ​ $ 48,236 Operating lease income relating to lease payments ​ 34,791 ​ 27,552 ​ 3,923 Operating lease income relating to variable lease payments ​ 5,710 ​ 9,608 ​ — Lease, airport services and other ​ $ 66,305 ​ $ 82,698 ​ $ 52,159
Delta Connection Agreement
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of details of aircraft and agreements with other airlines	Delta Connection Agreements Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates Delta Connection Agreement (capacity purchase arrangement) ​ ● E175 ● CRJ 900 ● CRJ 700 ​ 71 39 6 ​ ● Individual aircraft have scheduled removal dates from 2021 to 2030 ● ​ Delta Connection Prorate Agreement (prorate arrangement) ​ ● CRJ 200 ​ 26 ​ ● Terminable with 30-day ​
United Express Agreements
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of details of aircraft and agreements with other airlines	United Express Agreements ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates United Express Agreements (capacity purchase arrangement) ​ ● E175 ● CRJ 700 ● CRJ 200 ​ 90 19 70 ​ ​ ● Individual aircraft have scheduled removal dates under the agreement between 2022 and 2029 ● ​ United Express Prorate Agreement (prorate arrangement) ​ ● CRJ 200 ​ ​ 34 ​ ● Terminable with 120-day ​
American Agreements
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of details of aircraft and agreements with other airlines	American Capacity Purchase Agreement ​ ​ ​ ​ ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates American Agreement (capacity purchase arrangement) ​ ● CRJ 700 ​ ​ 65 ​ ● ● ​
Alaska Capacity Purchase Agreement
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of details of aircraft and agreements with other airlines	Alaska Capacity Purchase Agreement ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Agreement Aircraft type ​ Number of Aircraft Term / Termination Dates Alaska Agreement (capacity purchase arrangement) ​ ● E175 ​ ​ 32 ​ ● ● ​
Aircraft
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Schedule of future minimum rental payments for operating leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 $ 43,573 2022 ​ 43,390 ​ 2023 ​ 42,837 ​ 2024 ​ 42,530 ​ 2025 ​ 39,082 ​ Thereafter ​ 155,089 ​ ​ ​ $ 366,501 ​

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting
Schedule of Company's segment data	The following represents the Company’s segment data for the years ended December 31, 2020, 2019 and 2018 (in thousands). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ SkyWest ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Airlines ​ ​ SkyWest Leasing ​ ​ Consolidated ​ Operating revenues ​ $ 1,636,762 ​ $ 490,344 ​ $ 2,127,106 ​ Operating expense ​ 1,716,808 ​ ​ 301,496 ​ ​ 2,018,304 ​ Depreciation and amortization expense ​ 221,216 ​ 253,743 ​ 474,959 ​ Interest expense ​ 12,381 ​ 110,792 ​ 123,173 ​ Segment profit (loss) (1) ​ (92,427) ​ 78,056 ​ (14,371) ​ Total assets ​ 2,804,259 ​ 4,083,363 ​ 6,887,622 ​ Capital expenditures (including non-cash) ​ 124,825 ​ 335,658 ​ 460,483 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ SkyWest ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Airlines ​ ​ ExpressJet ​ ​ SkyWest Leasing ​ ​ Consolidated Operating revenues ​ $ 2,478,681 ​ $ 24,050 ​ $ 469,232 ​ $ 2,971,963 ​ Operating expense ​ 2,214,632 ​ ​ 28,690 ​ ​ 216,383 ​ 2,459,705 ​ Depreciation and amortization expense ​ 168,246 ​ 971 ​ 198,881 ​ 368,098 ​ Special items ​ ​ 18,508 ​ ​ 3,361 ​ ​ — ​ ​ 21,869 ​ Interest expense ​ 13,525 ​ — ​ 114,230 ​ 127,755 ​ Segment profit (loss) (1) ​ 250,524 ​ (4,640) ​ 138,619 ​ 384,503 ​ Total assets ​ 2,728,964 ​ — ​ 3,928,165 ​ 6,657,129 ​ Capital expenditures (including non-cash) ​ 270,191 ​ — ​ 576,279 ​ 846,470 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2018 ​ ​ ​ ​ SkyWest ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Airlines ​ ​ ExpressJet ​ ​ SkyWest Leasing ​ ​ Consolidated Operating revenues ​ $ 2,346,251 ​ $ 564,202 ​ $ 311,226 ​ $ 3,221,679 ​ Operating expense ​ 2,022,560 ​ ​ 577,608 ​ ​ 147,231 ​ 2,747,399 ​ Depreciation and amortization expense ​ 155,511 ​ 37,290 ​ 141,788 ​ 334,589 ​ Interest expense ​ 17,021 ​ 2,340 ​ 101,048 ​ 120,409 ​ Segment profit (loss) (1) ​ 306,670 ​ (15,746) ​ 62,947 ​ 353,871 ​ Total assets ​ 2,531,707 ​ 279,303 ​ 3,502,202 ​ 6,313,212 ​ Capital expenditures (including non-cash) ​ 149,731 ​ 10,137 ​ 996,408 ​ 1,156,276 ​ (1) Segment profit is operating income less interest expense

Long-term Debt (Tables)

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Long-term Debt
Schedule of long-term debt	Long-term debt consisted of the following as of December 31, 2020 and 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2020 ​ 2019 Notes payable to a financing company, due in semi-annual installments, with a fixed interest rate of 3.25% through 2021, secured by aircraft ​ $ 6,205 ​ $ 18,412 ​ Notes payable to banks, due in semi-annual installments plus interest at 6.24% to 6.51% through 2021, secured by aircraft ​ 7,608 ​ 22,557 ​ Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.68% to 6.86% through 2029, secured by aircraft ​ 424,407 ​ 438,878 ​ Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.08% through 2032, secured by aircraft ​ ​ 2,618,777 ​ ​ 2,537,676 ​ Notes payable to bank, due in monthly installments interest based on LIBOR plus interest spread at 2.65% through 2021 ​ ​ 13,795 ​ ​ — ​ Notes payable to US Government, interest due quarterly based on LIBOR plus interest spread currently at 3.22% through 2025, secured by parts and engines ​ ​ 60,000 ​ ​ — ​ Notes payable to US Government, interest due quarterly at 1.00% through 2025 and based on SOFR plus spread from 2025 through 2030, unsecured ​ 105,210 ​ — ​ Long-term debt ​ $ 3,236,002 ​ $ 3,017,523 ​ Current portion of long-term debt ​ (406,005) ​ (367,954) ​ Less long-term portion of unamortized debt issue cost, net ​ ​ (28,459) ​ ​ (20,580) ​ Long-term debt, net of current maturities and debt issue costs ​ $ 2,801,538 ​ $ 2,628,989 ​ ​ ​ ​ ​ ​ ​ ​ ​ Current portion of long-term debt ​ 406,005 ​ 367,954 ​ Less current portion of unamortized debt issue cost, net ​ ​ (3,847) ​ ​ (3,828) ​ Current portion of long-term debt, net of debt issue costs ​ $ 402,158 ​ $ 364,126 ​
Schedule of maturities of long-term debt	The aggregate amounts of principal maturities of long-term debt as of December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ 2021 $ 406,005 2022 ​ 407,554 ​ 2023 ​ 418,048 ​ 2024 ​ 372,322 ​ 2025 ​ 447,251 ​ Thereafter ​ 1,184,822 ​ ​ ​ $ 3,236,002 ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Taxes
Schedule of components of provision (benefit) for income taxes	The provision for income taxes includes the following components (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Current tax provision (benefit): ​ ​ ​ ​ Federal ​ $ (4,397) ​ $ (4,395) ​ $ (21,598) ​ State ​ (875) ​ 891 ​ 1,465 ​ Foreign ​ ​ — ​ ​ — ​ ​ 1,575 ​ ​ ​ (5,272) ​ (3,504) ​ (18,558) ​ Deferred tax provision (benefit): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ 6,659 ​ 95,655 ​ 92,250 ​ State ​ (199) ​ 14,055 ​ 12,250 ​ ​ ​ 6,460 ​ 109,710 ​ 104,500 ​ Provision (benefit) for income taxes ​ $ 1,188 ​ $ 106,206 ​ $ 85,942 ​
Schedule of income tax rate reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Current tax provision (benefit): ​ ​ ​ ​ Federal ​ $ (4,397) ​ $ (4,395) ​ $ (21,598) ​ State ​ (875) ​ 891 ​ 1,465 ​ Foreign ​ ​ — ​ ​ — ​ ​ 1,575 ​ ​ ​ (5,272) ​ (3,504) ​ (18,558) ​ Deferred tax provision (benefit): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ 6,659 ​ 95,655 ​ 92,250 ​ State ​ (199) ​ 14,055 ​ 12,250 ​ ​ ​ 6,460 ​ 109,710 ​ 104,500 ​ Provision (benefit) for income taxes ​ $ 1,188 ​ $ 106,206 ​ $ 85,942 ​
Schedule of components of the net deferred tax assets and liabilities	The significant components of the Company’s net deferred tax assets and liabilities as of December 31, 2020 and 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ ​ 2020 ​ 2019 Deferred tax assets: ​ ​ ​ Accrued benefits ​ $ 19,668 ​ $ 20,848 ​ Net operating loss carryforward ​ 229,815 ​ 358,685 ​ AMT credit carryforward ​ — ​ 4,397 ​ Aircraft credits ​ 12,765 ​ 9,114 ​ Deferred revenue ​ ​ 27,076 ​ ​ — ​ Accrued reserves and other ​ 34,816 ​ 17,225 ​ Total deferred tax assets ​ 324,140 ​ 410,269 ​ Valuation allowance ​ — ​ (892) ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Accelerated depreciation ​ (950,071) ​ (1,032,957) ​ Total deferred tax liabilities ​ (950,071) ​ (1,032,957) ​ Net deferred tax liability ​ $ (625,931) ​ $ (623,580) ​
Schedule of unrecognized tax benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits for the year ended December 31, 2020, 2019 and 2018 is as follows (in thousands) : ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Unrecognized tax benefits at the beginning of year $ 14,620 $ 14,553 $ 2,223 Gross increases - current year tax positions ​ ​ — ​ ​ — ​ ​ 13,899 Gross increases - prior year tax positions ​ 360 ​ 67 ​ — Gross decreases - prior year tax positions ​ ​ — ​ ​ — ​ ​ (1,569) Unrecognized tax benefits at end of year ​ $ 14,980 ​ $ 14,620 ​ $ 14,553 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and penalties in year-end balance ​ $ 427 ​ $ 67 ​ $ —

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases
Summary of related terms and discount rates	The table below presents lease related terms and discount rates as of December 31, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2020 Weighted-average remaining lease term ​ Operating leases ​ ​ 6.50 years ​ Weighted-average discount rate ​ ​ ​ Operating leases ​ ​ 6.1% ​
Summary of lease costs	The Company’s lease costs for 2020 and 2019 included the following components (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31, ​ 2020 2019 Operating lease cost $ 94,915 $ 104,011 Variable and short-term lease cost ​ 4,619 ​ 5,232 Sublease income ​ ​ (6,304) ​ ​ (1,436) Total lease cost $ 93,230 $ 107,807
Schedule of future minimum rental payments for operating leases	The following table summarizes future minimum rental payments primarily related to leased aircraft required under operating leases that had initial or remaining non-cancelable lease terms as of December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ 2021 $ 85,869 2022 ​ 77,780 ​ 2023 ​ 69,530 ​ 2024 ​ 28,091 ​ 2025 ​ 15,751 ​ Thereafter ​ 82,719 ​ ​ ​ $ 359,740 ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Measurements
Schedule of assets measured at fair value on a recurring basis	As of December 31, 2020, the Company held certain assets that are required to be measured at fair value on a recurring basis. Assets measured at fair value on a recurring basis are summarized below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of December 31, 2020 ​ ​ Total Level 1 Level 2 Level 3 Marketable Securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Bonds and bond funds ​ $ 117,928 ​ $ — ​ $ 117,928 ​ $ — ​ Commercial paper ​ 492,257 ​ — ​ 492,257 ​ — ​ ​ ​ $ 610,185 ​ $ — ​ $ 610,185 ​ $ — ​ Cash, Cash Equivalents and Restricted Cash ​ ​ 215,723 ​ 215,723 ​ — ​ — ​ Total Assets Measured at Fair Value ​ $ 825,908 ​ $ 215,723 ​ $ 610,185 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements as of December 31, 2019 ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Marketable Securities ​ ​ ​ ​ ​ Bonds and bond funds ​ $ 267,243 ​ $ — ​ $ 267,243 ​ $ — ​ Commercial paper ​ 165,723 ​ — ​ 165,723 ​ — ​ ​ ​ $ 432,966 ​ $ — ​ $ 432,966 ​ $ — ​ Cash, Cash Equivalents and Restricted Cash ​ ​ 87,206 ​ 87,206 ​ — ​ — ​ Total Assets Measured at Fair Value ​ $ 520,172 ​ $ 87,206 ​ $ 432,966 ​ $ — ​

Special Items (Tables)

Special Items (Tables)	12 Months Ended
	Dec. 31, 2020
Special Items
Summary of the components of special items	The following table summarizes the components of the Company's special items, for the year ended December 31, 2020, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ 2020 2019 2018 Special items: ​ ​ ​ ​ ​ ​ ​ ​ ​ Parts Credit 1 ​ $ — ​ $ 18,508 ​ $ — Employee severance 2 ​ — ​ ​ 3,361 ​ — Total special items ​ $ — ​ $ 21,869 ​ $ — (1) The Company terminated an agreement with an aircraft manufacturer that obligated the Company to future aircraft lease return conditions on aircraft the Company leased. In conjunction with the terminated agreement, the aircraft manufacturer released the Company from the future aircraft lease return obligations and the Company agreed to terminate aircraft part credits previously issued by the manufacturer to the Company. As a result of the terminated agreement, the Company recorded a non-cash expense of $18.5 million (pre-tax) during 2019 to write-off the terminated aircraft part credits, which was reflected as a special items operating expense in the consolidated statement of comprehensive income. These special items are reflected in the SkyWest Airlines operating expenses under Note 3 Segment Reporting . ​ (2) During 2019, the Company incurred $3.4 million of employee severance related costs associated with the sale of ExpressJet that are also reflected in special items. These special items are reflected in the ExpressJet operating expenses under Note 3 Segment Reporting .

Capital Transactions (Tables)

Capital Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Schedule of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 ​ 2018 ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ Aggregate ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ Remaining ​ Intrinsic ​ ​ ​ Average ​ ​ ​ Average ​ ​ Number of ​ Exercise ​ Contractual ​ Value ​ Number of ​ Exercise ​ Number of ​ Exercise ​ ​ Options ​ Price ​ Term ​ ($000) ​ Options ​ Price ​ Options ​ Price Outstanding at beginning of year 60,231 ​ 14.74 3.1 years $ 3,005.1 300,580 $ 13.70 458,103 $ 13.73 ​ Granted — ​ — ​ ​ ​ ​ ​ — ​ — — ​ — ​ Exercised (2,578) ​ 14.78 ​ ​ ​ ​ ​ (232,514) ​ 13.36 (157,523) ​ 13.80 ​ Cancelled — ​ — ​ ​ ​ ​ ​ (7,835) ​ 15.86 — ​ — ​ Outstanding at end of year 57,653 ​ 14.74 2.1 years $ 1,474.5 60,231 ​ 14.74 300,580 ​ 13.70 ​ Exercisable at December 31, 2020 57,653 ​ ​ 14.74 ​ 2.1 years $ 1,474.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2019 60,231 ​ ​ 14.74 ​ 3.1 years $ 3,005.1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of stock options outstanding	The following table summarizes information about the Company’s stock options outstanding at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options Outstanding ​ Options Exercisable ​ ​ ​ ​ ​ ​ Weighted Average ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number ​ Remaining ​ Weighted Average ​ Number ​ Weighted Average Range of Exercise Prices ​ Outstanding ​ Contractual Life ​ Exercise Price ​ Exercisable ​ Exercise Price $13.00 to $13.99 2,034 0.1 years $ 13.51 ​ 2,034 $ 13.51 ​ $14.00 to $15.00 55,619 1.1 years ​ 14.78 55,619 ​ 14.78 ​ $13.00 to $15.00 57,653 1.1 years ​ $ 14.74 57,653 ​ $ 14.74 ​
Schedule of restricted stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ Grant-Date Fair ​ ​ Number of RSUs ​ ​ Value Non-vested RSUs outstanding at December 31, 2017 815,590 ​ $ 18.35 ​ Granted 115,044 ​ 53.40 ​ Vested (330,580) ​ 13.57 ​ Cancelled (24,273) ​ 27.77 ​ Non-vested RSUs outstanding at December 31, 2018 575,781 ​ $ 27.71 ​ Granted 104,120 ​ 48.65 ​ Vested (251,853) ​ 14.79 ​ Cancelled (143,362) ​ 30.85 ​ Non-vested RSUs outstanding at December 31, 2019 284,686 ​ $ 45.21 ​ Granted 82,505 ​ 61.45 ​ Vested (103,231) ​ 35.81 ​ Cancelled (25,983) ​ 52.31 ​ Non-vested RSUs outstanding at December 31, 2020 237,977 ​ $ 54.15 ​
Performance stock units
Schedule of non-vested stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ Grant-Date ​ ​ Number of PSUs ​ ​ Fair Value Non-vested PSUs outstanding at December 31, 2017 468,576 ​ $ 19.70 Granted 90,264 ​ 53.41 Additional PSUs awarded from the 2015 grant 92,335 ​ 13.62 Vested (277,029) ​ 13.62 Cancelled (3,229) ​ 30.09 Non-vested PSUs outstanding at December 31, 2018 370,917 ​ $ 30.84 Granted 87,864 ​ 48.81 Additional PSUs awarded from the 2016 grant 67,853 ​ 14.80 Vested (203,582) ​ 14.80 Cancelled (89,481) ​ 34.70 Non-vested PSUs outstanding at December 31, 2019 233,571 ​ $ 45.44 Granted 69,132 ​ 61.45 Additional PSUs awarded from the 2017 grant 83,042 ​ 35.81 Vested (166,084) ​ 35.81 Cancelled (23,052) ​ 53.66 Non-vested PSUs outstanding at December 31, 2020 196,609 ​ $ 54.17

Retirement Plans and Employee_2

Retirement Plans and Employee Stock Purchase Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Plans and Employee Stock Purchase Plans
Schedule of purchases made under the 2009 Employee Stock Purchase Plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, ​ ​ 2020 ​ 2019 ​ 2018 Number of shares purchased ​ 65,512 ​ 65,148 ​ 60,950 ​ Average price of shares purchased ​ $ 42.45 ​ $ 48.58 ​ $ 49.85 ​

Quarterly Financial Data (Una_2

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data (Unaudited)
Schedule of Quarterly Financial Data (Unaudited)	Unaudited summarized financial data by quarter for 2020 and 2019 is as follows (in thousands, except per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2020 ​ ​ First ​ Second ​ Third ​ Fourth ​ ​ ​ ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year Operating revenues $ 729,936 $ 350,039 $ 457,493 $ 589,638 $ 2,127,106 ​ Operating income ​ 66,321 ​ (4,403) ​ 74,553 ​ (27,669) ​ 108,802 ​ Net income ​ 29,988 ​ (25,715) ​ 33,662 ​ (46,450) ​ (8,515) ​ Net income per common share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ 0.60 ​ (0.51) ​ 0.67 ​ (0.93) ​ (0.17) ​ Diluted ​ 0.59 ​ (0.51) ​ 0.66 ​ (0.93) ​ (0.17) ​ Weighted average common shares: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic: ​ 50,277 ​ 50,140 ​ 50,181 ​ 50,181 ​ 50,195 ​ Diluted: ​ 50,559 ​ 50,140 ​ 50,622 ​ 50,181 ​ 50,195 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year ended December 31, 2019 ​ ​ First ​ Second ​ Third ​ Fourth ​ ​ ​ ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year Operating revenues $ 723,694 $ 744,383 $ 760,295 $ 743,591 $ 2,971,963 ​ Operating income ​ 96,419 ​ 144,093 ​ 146,441 ​ 125,305 ​ ​ 512,258 ​ Net income (1) ​ 88,181 ​ 88,052 ​ 91,339 ​ 72,527 ​ ​ 340,099 ​ Net income per common share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ 1.71 ​ 1.72 ​ 1.80 ​ 1.44 ​ ​ 6.68 ​ Diluted ​ 1.69 ​ 1.71 ​ 1.79 ​ 1.43 ​ ​ 6.62 ​ Weighted average common shares: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic: ​ 51,440 ​ 51,145 ​ 50,746 ​ 50,395 ​ ​ 50,932 ​ Diluted: ​ 52,098 ​ 51,477 ​ 51,129 ​ 50,796 ​ ​ 51,375 ​

Nature of Operations and Summ_4

Nature of Operations and Summary of Significant Accounting Policies - Aircraft Fleet (Details)	12 Months Ended
	Dec. 31, 2020aircraft
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of daily departures	1,770
Number of aircraft held by entity	601
CRJ 200
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	206
Number of seats on aircraft	50
CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	154
CRJ 700 | Minimum
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of seats on aircraft	65
CRJ 700 | Maximum
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of seats on aircraft	76
CRJ 900
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	48
CRJ 900 | Minimum
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of seats on aircraft	65
CRJ 900 | Maximum
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of seats on aircraft	76
E175
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	193
E175 | Minimum
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of seats on aircraft	65
E175 | Maximum
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of seats on aircraft	76
Delta
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	142
Percentage of aggregate capacity operated	47.10%
Delta | CRJ 200
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	26
Delta | CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	6
Delta | CRJ 900
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	39
Delta | E175
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	71
United
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	213
Percentage of aggregate capacity operated	31.40%
United | CRJ 200
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	104
United | CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	19
United | E175
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	90
American
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	65
Percentage of aggregate capacity operated	14.40%
American | CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	65
Alaska
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	32
Percentage of aggregate capacity operated	7.10%
Alaska | E175
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	32
Aircraft in scheduled service
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	452
Aircraft in scheduled service | CRJ 200
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	130
Aircraft in scheduled service | CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	90
Aircraft in scheduled service | CRJ 900
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	39
Aircraft in scheduled service | E175
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	193
Leased to third parties
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	41
Leased to third parties | CRJ 200
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	2
Leased to third parties | CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	34
Leased to third parties | CRJ 900
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	5
Other
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	108
Other | CRJ 200
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	74
Other | CRJ 700
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	30
Other | CRJ 900
Nature of Operations and Summary of Significant Accounting Policies [Line Items]
Number of aircraft held by entity	4

Nature of Operations and Summ_5

Nature of Operations and Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Nature of Operations and Summary of Significant Accounting Policies
Restricted cash	$ 0	$ 0

Nature of Operations and Summ_6

Nature of Operations and Summary of Significant Accounting Policies - Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total cash and cash equivalents	$ 215,723	$ 87,206	$ 328,384	$ 181,792
Amortized Cost	610,185	432,966
Fair market value	610,185	432,966
Total Assets Measured at Fair Value - Amortized cost	825,908	520,172
Total cash and cash equivalents and available for sale securities, fair market value	$ 825,908	520,172
Marketable Securities
Maximum period for redemption	1 year
Bonds and bond funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 117,928	267,243
Fair market value	117,928	267,243
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	492,257	165,723
Fair market value	$ 492,257	$ 165,723

Nature of Operations and Summ_7

Nature of Operations and Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Inventories
Inventory allowance	$ 19.7	$ 15.9

Nature of Operations and Summ_8

Nature of Operations and Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Aircraft, rotable spares, and spare engines | Maximum
Property and Equipment
Depreciable Life	22 years
Residual Value (as a percent)	20.00%
Ground equipment
Property and Equipment
Residual Value (as a percent)	0.00%
Ground equipment | Maximum
Property and Equipment
Depreciable Life	10 years
Office equipment
Property and Equipment
Residual Value (as a percent)	0.00%
Office equipment | Maximum
Property and Equipment
Depreciable Life	7 years
Leasehold improvements
Property and Equipment
Residual Value (as a percent)	0.00%
Leasehold improvements | Maximum
Property and Equipment
Depreciable Life	15 years
Buildings
Property and Equipment
Residual Value (as a percent)	0.00%
Buildings | Minimum
Property and Equipment
Depreciable Life	20 years
Buildings | Maximum
Property and Equipment
Depreciable Life	39 years 6 months

Nature of Operations and Summ_9

Nature of Operations and Summary of Significant Accounting Policies - Long-Lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Impairment of Long Lived and Intangible Assets
Property and equipment and related assets	$ 5,362,048	$ 5,394,681
Impairment of long-lived assets	$ 0	$ 0	$ 0

Nature of Operations and Sum_10

Nature of Operations and Summary of Significant Accounting Policies - Capitalized Interest and Maintenance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Capitalized Interest
Capitalized interest costs	$ 1.7	$ 1.6	$ 1.5
Long-lived maintenance assets written off	$ 3.7

Nature of Operations and Sum_11

Nature of Operations and Summary of Significant Accounting Policies - Flying Agreements (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)aircraft	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Agreements with other airlines
Percentage of ASMs flown under fixed-fee arrangements									87.00%
Percentage of ASMs flown under pro-rate arrangements									13.00%
Revenues [Abstract]
Operating revenues	$ 589,638	$ 457,493	$ 350,039	$ 729,936	$ 743,591	$ 760,295	$ 744,383	$ 723,694	$ 2,127,106	$ 2,971,963	$ 3,221,679
Rental income under operating leases
Operating lease revenue									34,791
Operating lease income relating to lease payments										27,552	3,923
Operating lease income relating to variable lease payments									5,710	9,608
Future minimum rental income
2021	43,573								43,573
2022	43,390								43,390
2023	42,837								42,837
2024	42,530								42,530
2025	39,082								39,082
Thereafter	155,089								155,089
Total	366,501								366,501
Property and equipment and related assets	5,362,048				5,394,681				5,362,048	5,394,681
Deferred recognizing revenue									110,728
Accounts receivable	34,500				83,000				34,500	83,000
Gross receivables current	56,100								56,100
Gross receivables Non-current	157,400								157,400
Balance				$ 15,388					15,388
Additions to credit loss reserve									30,837
Balance	46,225				15,388				$ 46,225	15,388
Sky West Airlines Inc | Delta Connection Agreement
Future minimum rental income
Agreement term									5 years 8 months 12 days
Sky West Airlines Inc | Delta Connection Prorate Agreement
Future minimum rental income
Notice period for termination of agreement									30 days
Sky West Airlines Inc | United Express Agreements
Future minimum rental income
Agreement term									4 years 10 months 24 days
Sky West Airlines Inc | United Express Prorate Agreement
Future minimum rental income
Notice period for termination of agreement									120 days
Third Party Lease
Future minimum rental income
Property and equipment and related assets	271,100								$ 271,100
CRJ 200
Future minimum rental income
Number of seats on aircraft | aircraft									50
CRJ 200 | Sky West Airlines Inc | Delta Connection Prorate Agreement
Future minimum rental income
Number of aircraft | aircraft									26
CRJ 200 | Sky West Airlines Inc | United Express Agreements
Future minimum rental income
Number of aircraft | aircraft									70
CRJ 200 | Sky West Airlines Inc | United Express Prorate Agreement
Future minimum rental income
Number of aircraft | aircraft									34
CRJ 700 | Minimum
Future minimum rental income
Number of seats on aircraft | aircraft									65
CRJ 700 | Maximum
Future minimum rental income
Number of seats on aircraft | aircraft									76
CRJ 700 | American Capacity Purchase Agreement
Future minimum rental income
Number of aircraft | aircraft									65
Agreement term									3 years 3 months 18 days
CRJ 700 | Sky West Airlines Inc | Delta Connection Agreement
Future minimum rental income
Number of aircraft | aircraft									6
CRJ 700 | Sky West Airlines Inc | United Express Agreements
Future minimum rental income
Number of aircraft | aircraft									19
CRJ 700 | American
Future minimum rental income
Number of aircraft | aircraft									25
CRJ 900 | Minimum
Future minimum rental income
Number of seats on aircraft | aircraft									65
CRJ 900 | Maximum
Future minimum rental income
Number of seats on aircraft | aircraft									76
CRJ 900 | Sky West Airlines Inc | Delta Connection Agreement
Future minimum rental income
Number of aircraft | aircraft									39
CRJ 900 | Delta
Future minimum rental income
Number of aircraft | aircraft									1
E175 | Minimum
Future minimum rental income
Number of seats on aircraft | aircraft									65
E175 | Maximum
Future minimum rental income
Number of seats on aircraft | aircraft									76
E175 | Alaska Capacity Purchase Agreement
Future minimum rental income
Number of aircraft | aircraft									32
Agreement term									8 years 2 months 12 days
E175 | Sky West Airlines Inc | Delta Connection Agreement
Future minimum rental income
Number of aircraft | aircraft									71
E175 | Sky West Airlines Inc | United Express Agreements
Future minimum rental income
Number of aircraft | aircraft									90
E175 | American
Future minimum rental income
Number of aircraft | aircraft									20
Flying agreements
Revenues [Abstract]
Operating revenues									$ 2,060,801	2,889,265	3,169,520
Future minimum rental income
Accounts receivable	$ 27,500				$ 58,800				27,500	58,800
Flight operations
Revenues [Abstract]
Operating revenues									945,008	1,538,062	1,856,253
Aircraft lease and fixed revenue
Revenues [Abstract]
Operating revenues									846,933	830,247	814,518
Prorate agreements
Revenues [Abstract]
Operating revenues									268,860	520,956	498,749
Airport customer service and other revenue
Rental income under operating leases
Operating lease revenue									25,804	45,538	48,236
Lease, airport services and other
Rental income under operating leases
Total operating lease income									$ 66,305	$ 82,698	$ 52,159

Nature of Operations and Sum_12

Nature of Operations and Summary of Significant Accounting Policies - Net Income (Loss) Per Common Share and Fair Value (Details) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares	Sep. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2020USD ($)$ / sharesshares	Mar. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Sep. 30, 2019USD ($)$ / sharesshares	Jun. 30, 2019USD ($)$ / sharesshares	Mar. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2020USD ($)segment$ / sharesshares	Dec. 31, 2019USD ($)segment$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares
Net Income (Loss) Per Common Share
Number of outstanding units not included in computation of Diluted EPS (in shares)									1,074,375	150,000	207,000
Numerator:
Net income (loss) | $	$ (46,450)	$ 33,662	$ (25,715)	$ 29,988	$ 72,527	$ 91,339	$ 88,052	$ 88,181	$ (8,515)	$ 340,099	$ 280,372
Denominator:
Basic earnings per share weighted average shares (in shares)	50,181,000	50,181,000	50,140,000	50,277,000	50,395,000	50,746,000	51,145,000	51,440,000	50,195,000	50,932,000	51,914,000
Dilution due to stock options and restricted stock units (in shares)										443,000	957,000
Diluted earnings per share weighted average shares	50,181,000	50,622,000	50,140,000	50,559,000	50,796,000	51,129,000	51,477,000	52,098,000	50,195,000	51,375,000	52,871,000
Basic earnings (loss) per share (in dollars per share) | $ / shares	$ (0.93)	$ 0.67	$ (0.51)	$ 0.60	$ 1.44	$ 1.80	$ 1.72	$ 1.71	$ (0.17)	$ 6.68	$ 5.40
Diluted earnings (loss) per share (in dollars per share) | $ / shares	$ (0.93)	$ 0.66	$ (0.51)	$ 0.59	$ 1.43	$ 1.79	$ 1.71	$ 1.69	$ (0.17)	$ 6.62	$ 5.30
Fair Value of Financial Instruments
Fair value of long-term debt | $	$ 3,244,000				$ 3,049,100				$ 3,244,000	$ 3,049,100
Total long-term debt | $	$ 3,236,002				$ 3,017,523				$ 3,236,002	$ 3,017,523
Segment Reporting
Number of operating segments | segment										3
Number of reporting segments | segment									2

Nature of Operations and Sum_13

Nature of Operations and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit loss		$ 30,837
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit loss	$ 11,600

Impact of the COVID-19 Pandem_2

Impact of the COVID-19 Pandemic (Details) $ / shares in Units, $ in Thousands	Jan. 22, 2019	Jun. 30, 2020aircraft	Dec. 31, 2020USD ($)itemaircraft$ / sharesshares	Oct. 28, 2020USD ($)	Sep. 30, 2020USD ($)	Apr. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Unusual or Infrequent Item, or Both [Line Items]
Liquid Assets			$ 1,530,400
Cash and Marketable Securities			825,900
Line of credit facility, reduction of amount available			39,500
Borrowed amount			$ 3,236,002				$ 3,017,523
Interest rate (as a percent)	6.85%
COVID-19
Unusual or Infrequent Item, or Both [Line Items]
Decrease in departures (as a percent)			30.50%
Decrease in block hours (as a percent)			33.50%
Maximum
Unusual or Infrequent Item, or Both [Line Items]
CARES Act, secured loans to airline industry			$ 25,000,000
PSP agreement
Unusual or Infrequent Item, or Both [Line Items]
Grants receivable			450,700		$ 450,700	$ 438,000
Proceeds			$ 345,500
CRJ 200 | Sky West Airlines Inc
Unusual or Infrequent Item, or Both [Line Items]
Number of aircraft removed from service | aircraft			55
CRJ 200 | Sky West Airlines Inc | American Prorate Agreement
Unusual or Infrequent Item, or Both [Line Items]
Number of aircraft removed from service | aircraft		7
Grant | PSP agreement
Unusual or Infrequent Item, or Both [Line Items]
Principal amount			$ 345,500
Unsecured term loan | PSP agreement
Unusual or Infrequent Item, or Both [Line Items]
Principal amount			$ 105,200
Debt term			10 years
Unsecured term loan | First five years | PSP agreement
Unusual or Infrequent Item, or Both [Line Items]
Interest rate (as a percent)			1.00%
Unsecured term loan | Final five years | PSP agreement
Unusual or Infrequent Item, or Both [Line Items]
Interest rate (as a percent)			2.00%
Secured loan
Unusual or Infrequent Item, or Both [Line Items]
Borrowed amount			$ 60,000
Number of subsequent borrowings | item			2
Interest rate (as a percent)			3.22%
Warrants to purchase shares | shares			211,416
Warrants exercise price | $ / shares			$ 28.38
Warrant term			5 years
Maximum borrowing capacity				$ 725,000	573,000
Secured loan | COVID-19
Unusual or Infrequent Item, or Both [Line Items]
Liquid Assets			$ 665,000
Secured loan | LIBOR
Unusual or Infrequent Item, or Both [Line Items]
Basis spread on variable rate			3.00%
Secured loan
Unusual or Infrequent Item, or Both [Line Items]
Borrowed amount			$ 60,000
Number of subsequent borrowings | aircraft			2
Warrants to purchase shares | shares			211,416
Warrants exercise price | $ / shares			$ 28.38
Warrant term			5 years
Maximum borrowing capacity				$ 725,000	$ 573,000
Warrant Shares | PSP agreement
Unusual or Infrequent Item, or Both [Line Items]
Warrants to purchase shares | shares			370,720
Warrants exercise price | $ / shares			$ 28.38
Warrant term			5 years

Segment Reporting (Details)

Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2020USD ($)segment	Dec. 31, 2019USD ($)segment	Dec. 31, 2018USD ($)
Segment Reporting
Number of operating segments | segment										3
Number of reporting segments | segment									2
Operating revenues	$ 589,638	$ 457,493	$ 350,039	$ 729,936	$ 743,591	$ 760,295	$ 744,383	$ 723,694	$ 2,127,106	$ 2,971,963	$ 3,221,679
Operating expense									2,018,304	2,459,705	2,747,399
Depreciation and amortization expense									474,959	368,098	334,589
Special items								$ 21,900		21,869
Interest expense									123,173	127,755	120,409
Segment profit (loss)									(14,371)	384,503	353,871
Total assets	6,887,622				6,657,129				6,887,622	6,657,129	6,313,212
Capital expenditures (including non-cash)									460,483	846,470	1,156,276
SkyWest Airlines
Segment Reporting
Operating revenues									1,636,762	2,478,681	2,346,251
Operating expense									1,716,808	2,214,632	2,022,560
Depreciation and amortization expense									221,216	168,246	155,511
Special items										18,508
Interest expense									12,381	13,525	17,021
Segment profit (loss)									(92,427)	250,524	306,670
Total assets	2,804,259				2,728,964				2,804,259	2,728,964	2,531,707
Capital expenditures (including non-cash)									124,825	270,191	149,731
ExpressJet Airlines Inc
Segment Reporting
Operating revenues										24,050	564,202
Operating expense										28,690	577,608
Depreciation and amortization expense										971	37,290
Special items										3,361
Interest expense											2,340
Segment profit (loss)										(4,640)	(15,746)
Total assets											279,303
Capital expenditures (including non-cash)											10,137
SkyWest Leasing
Segment Reporting
Operating revenues									490,344	469,232	311,226
Operating expense									301,496	216,383	147,231
Depreciation and amortization expense									253,743	198,881	141,788
Interest expense									110,792	114,230	101,048
Segment profit (loss)									78,056	138,619	62,947
Total assets	$ 4,083,363				$ 3,928,165				4,083,363	3,928,165	3,502,202
Capital expenditures (including non-cash)									$ 335,658	$ 576,279	$ 996,408

Long-term Debt (Details)

Long-term Debt (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)aircraft$ / sharesshares	Oct. 28, 2020USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Total long-term debt	$ 3,236,002			$ 3,017,523
Current portion of long-term debt	(406,005)			(367,954)
Less long-term portion of unamortized debt issue cost, net	(28,459)			(20,580)
Long-term debt, net of current maturities and debt issue costs	2,801,538			2,628,989
Current portion of long-term debt	406,005			367,954
Less current portion of unamortized debt issue cost, net	(3,847)			(3,828)
Current portion of long-term debt, net of debt issue costs	$ 402,158			$ 364,126
Effective interest rate (as a percent)	4.00%			4.20%
Aggregate amounts of principal maturities of long-term debt
2021	$ 406,005
2022	407,554
2023	418,048
2024	372,322
2025	447,251
Thereafter	1,184,822
Repayment of debt in cash	30,100
Total repayment of debt	30,100
Letters of credit	35,500			$ 8,800
Current borrowing capacity	39,500			66,200
Letters of credit and surety bonds outstanding with various banks and surety institutions	$ 61,100			61,700
E175
Debt Instrument [Line Items]
Number of aircraft delivered | aircraft	6
Purchase of aircraft financed through long-term debt	$ 107,700
Debt instrument, term	12 years
CRJ 700
Debt Instrument [Line Items]
Number of aircraft delivered | aircraft	21
Purchase of aircraft financed through long-term debt	$ 133,500
CRJ 700 | Quarterly Installments
Debt Instrument [Line Items]
Interest rate (as a percent)	3.50%
Number of aircraft delivered | aircraft	10
Debt instrument, term	7 years 6 months
CRJ 700 | Monthly Installments
Debt Instrument [Line Items]
Interest rate (as a percent)	4.00%
Number of aircraft delivered | aircraft	11
Debt instrument, term	5 years
Minimum | E175
Debt Instrument [Line Items]
Interest rate (as a percent)	2.30%
Maximum | E175
Debt Instrument [Line Items]
Interest rate (as a percent)	3.45%
Promissory note
Debt Instrument [Line Items]
Common stock value issued	$ 5,000
Warrants to purchase shares | shares	370,720
Warrants exercise price | $ / shares	$ 28.38
Warrant term	5 years
Long-term debt	$ 105,200
Principal amount	105,200
Secured loan
Debt Instrument [Line Items]
Total long-term debt	60,000
Common stock value issued	$ 3,200
Number of subsequent borrowings | aircraft	2
Warrants to purchase shares | shares	211,416
Warrants exercise price | $ / shares	$ 28.38
Warrant term	5 years
Aggregate amounts of principal maturities of long-term debt
Maximum borrowing capacity		$ 725,000	$ 573,000
Notes payable to a financing company, due in semi-annual installments, with a fixed interest rate of 3.25% through 2021, secured by aircraft
Debt Instrument [Line Items]
Interest rate (as a percent)	3.25%
Total long-term debt	$ 6,205			18,412
Notes payable to banks, due in semi-annual installments plus interest at 6.24% to 6.51% through 2021, secured by aircraft
Debt Instrument [Line Items]
Total long-term debt	$ 7,608			22,557
Notes payable to banks, due in semi-annual installments plus interest at 6.24% to 6.51% through 2021, secured by aircraft | Minimum
Debt Instrument [Line Items]
Interest rate (as a percent)	6.24%
Notes payable to banks, due in semi-annual installments plus interest at 6.24% to 6.51% through 2021, secured by aircraft | Maximum
Debt Instrument [Line Items]
Interest rate (as a percent)	6.51%
Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.68% to 6.86% through 2029, secured by aircraft
Debt Instrument [Line Items]
Total long-term debt	$ 424,407			438,878
Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.68% to 6.86% through 2029, secured by aircraft | Minimum
Debt Instrument [Line Items]
Interest rate (as a percent)	2.68%
Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.68% to 6.86% through 2029, secured by aircraft | Maximum
Debt Instrument [Line Items]
Interest rate (as a percent)	6.86%
Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.08% through 2032, secured by aircraft
Debt Instrument [Line Items]
Total long-term debt	$ 2,618,777			2,537,676
Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.08% through 2032, secured by aircraft | Minimum
Debt Instrument [Line Items]
Interest rate (as a percent)	2.33%
Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.08% through 2032, secured by aircraft | Maximum
Debt Instrument [Line Items]
Interest rate (as a percent)	5.08%
Notes payable to bank, due in monthly installments interest based on LIBOR plus interest spread at 2.65% through 2021
Debt Instrument [Line Items]
Total long-term debt	$ 13,795
Notes payable to US Government, interest due quarterly based on LIBOR plus interest spread currently at 3.22% through 2025, secured by parts and engines
Debt Instrument [Line Items]
Total long-term debt	$ 60,000
Basis spread on variable rate	3.22%
Notes payable to US Government, interest due quarterly at 1.00% through 2025 and based on SOFR plus spread from 2025 through 2030, unsecured
Debt Instrument [Line Items]
Total long-term debt	$ 105,210
Primarily related to acquisition of aircraft and certain spare engines
Debt Instrument [Line Items]
Total long-term debt	3,070,000			3,020,000
Line of credit
Aggregate amounts of principal maturities of long-term debt
Maximum borrowing capacity	75,000			75,000
Amount outstanding	$ 0			$ 0
LIBOR | Notes payable to bank, due in monthly installments interest based on LIBOR plus interest spread at 2.65% through 2021
Debt Instrument [Line Items]
Basis spread on variable rate	2.65%
LIBOR | Notes payable to US Government, interest due quarterly at 1.00% through 2025 and based on SOFR plus spread from 2025 through 2030, unsecured
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
LIBOR | Line of credit
Debt Instrument [Line Items]
Basis spread on variable rate	2.50%

Income Taxes - Provision (Detai

Income Taxes - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current tax provision (benefit):
Federal	$ (4,397)	$ (4,395)	$ (21,598)
State	(875)	891	1,465
Foreign			1,575
Total current tax provision (benefit)	(5,272)	(3,504)	(18,558)
Deferred tax provision (benefit):
Federal	6,659	95,655	92,250
State	(199)	14,055	12,250
Total deferred tax provision (benefit)	6,460	109,710	104,500
Provision for income taxes	$ 1,188	$ 106,206	$ 85,942

Income Taxes - Reconciliation (

Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statutory Federal income tax rate (as a percent)	21.00%	21.00%	21.00%
Reconciliation
Computed provision for income taxes at the statutory rate	$ (1,539)	$ 93,724	$ 76,926
State income tax provision, net of federal income tax benefit	173	15,645	12,711
Non-deductible expenses	2,539	3,934	1,956
Valuation allowance changes affecting the provision for income taxes	(892)	(517)	(1,187)
Foreign income taxes, net of federal & state benefit			1,192
Excess tax benefits from share based compensation	(1,434)	(3,525)	(4,548)
Other, net	2,341	(3,055)	(1,108)
Provision for income taxes	1,188	106,206	85,942
Deferred tax assets:
Accrued benefits	19,668	20,848
Net operating loss carryforward	229,815	358,685
AMT credit carryforward		4,397
Aircraft credits	12,765	9,114
Deferred revenue	27,076
Accrued reserves and other	34,816	17,225
Total deferred tax assets	324,140	410,269
Valuation allowance		(892)
Deferred tax liabilities:
Accelerated depreciation	(950,071)	(1,032,957)
Total deferred tax liabilities	(950,071)	(1,032,957)
Net deferred tax liability	(625,931)	(623,580)
Accounting Standards Update 2016-09
Reconciliation
Benefit from share-based compensation	1,400	3,500	4,500
ExpressJet | State
Reconciliation
Valuation allowance	$ 900	$ 500	$ 1,200

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Losses and Tax Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net operating losses
Statutory Federal income tax rate (as a percent)	21.00%	21.00%	21.00%
Alternative minimum tax credit which does not expire		$ 4.4
Federal
Net operating losses
Operating loss carryforward	$ 987	1,581.1
Estimated effective tax rate on net operating losses	21.00%
State
Net operating losses
Operating loss carryforward	$ 653.1	$ 766.4
Estimated effective tax rate on net operating losses	3.45%

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Unrecognized tax benefits at the beginning of year	$ 14,620,000	$ 14,553,000	$ 2,223,000
Gross increases - current year tax positions			13,899,000
Gross increases - prior year tax positions	360,000	67,000
Gross decreases - prior year tax positions			(1,569,000)
Unrecognized tax benefits at end of year	14,980,000	14,620,000	$ 14,553,000
Interest and penalties in year-end balance	427,000	67,000
Interest expense related to uncertain tax positions	$ 360,000	$ 67,000

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021aircraft	Dec. 31, 2020USD ($)employeeaircraft	Dec. 31, 2019USD ($)	Dec. 31, 2018
Concentration Risk and Significant Customers
Accrued workers' compensation liability | $		$ 20.7	$ 23.9
E175
Concentration Risk and Significant Customers
Commitment to purchase number of aircraft | aircraft		20
CRJ 700 | Subsequent event
Concentration Risk and Significant Customers
Commitment to purchase number of aircraft | aircraft	12
Revenue from rights, concentration risk | Customer concentration risk | Delta, United, and Continental Combined
Concentration Risk and Significant Customers
Concentration risk (as a percent)		76.40%	77.60%	81.40%
Full-time equivalent number of employees | Labor force concentration risk
Concentration Risk and Significant Customers
Number of employees | employee		12,502
SkyWest Airlines | Full-time equivalent number of employees | Unionized employees
Concentration Risk and Significant Customers
Approximate number of active employees | employee		0

Leases (Details)

Leases (Details) $ in Thousands	Jan. 01, 2019USD ($)	Dec. 31, 2020USD ($)aircraft	Dec. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Retained earnings		$ 2,052,006	$ 2,079,179
Operating lease right-of-use assets		282,362	336,009
Current maturities of lease liabilities		82,641	94,806
Noncurrent operating leases		205,845	259,237
Operating leases		$ 90,300
Weighted-average remaining lease term for operating leases		6 years 6 months
Weighted-average discount rate for operating leases		6.10%
Lease costs
Operating lease cost		$ 94,915	104,011
Variable and short-term lease cost		4,619	5,232
Sublease income		(6,304)	(1,436)
Total lease cost		$ 93,230	$ 107,807
Aircraft
Lessee, Lease, Description [Line Items]
Number of aircraft acquired | aircraft		41
Impairment charges	$ 13,100
Aircraft | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term		1 year
Aircraft | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term		10 years
Airport Facilities | Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term		1 month
Airport Facilities | Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term		36 years

Leases - Operating Leases (Deta

Leases - Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Future minimum rental payments required under operating leases
2021	$ 85,869
2022	77,780
2023	69,530
2024	28,091
Thereafter	15,751
Thereafter	82,719
Total	359,740
Total rental expense for non-cancelable aircraft operating leases			$ 154,900
Total rental expense for non-cancelable aircraft operating leases	65,300	$ 72,000
Minimum rental expense for airport station rents			$ 19,600
Minimum rental expense for airport station rents	$ 20,100	$ 23,100

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Measurements
Marketable securities	$ 610,185	$ 432,966
Total assets measured at fair value	825,908	520,172
Fair Value of Financial Instruments
Fair value of long-term debt	3,244,000	3,049,100
Recurring | Fair value
Fair Value Measurements
Marketable securities	610,185	432,966
Cash, Cash Equivalents and Restricted Cash	215,723	87,206
Total assets measured at fair value	825,908	520,172
Recurring | Fair value | Bonds and bond funds
Fair Value Measurements
Marketable securities	117,928	267,243
Recurring | Fair value | Commercial paper
Fair Value Measurements
Marketable securities	492,257	165,723
Recurring | Level 1
Fair Value Measurements
Cash, Cash Equivalents and Restricted Cash	215,723	87,206
Total assets measured at fair value	215,723	87,206
Recurring | Level 2
Fair Value Measurements
Marketable securities	610,185	432,966
Total assets measured at fair value	610,185	432,966
Recurring | Level 2 | Bonds and bond funds
Fair Value Measurements
Marketable securities	117,928	267,243
Recurring | Level 2 | Commercial paper
Fair Value Measurements
Marketable securities	$ 492,257	$ 165,723

Special Items (Details)

Special Items (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019
Special Items
Parts credit		$ 18,508
Employee severance		3,361
Total Special items	$ 21,900	$ 21,869

Capital Transactions - Preferre

Capital Transactions - Preferred Stock (Details) - shares	Dec. 31, 2020	Dec. 31, 2019
Preferred Stock
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock outstanding (in shares)	0

Capital Transactions - Stock Co

Capital Transactions - Stock Compensation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	May 04, 2010
Share-Based Compensation
Performance period	90 days
Compensation expenses
Stock based compensation expense	$ 6,802,000	$ 10,274,000	$ 13,105,000
Employee severance related costs	7,900,000
Forfeiture credit partially offset	$ 4,500,000
Director
Share-Based Compensation
Granted (in shares)	14,643	18,576
Granted (in dollars per share)	$ 61.45	$ 48.45	$ 53.40
Number of shares
Granted (in shares)	14,643	18,576
Weighted Average Grant-Date Fair Value
Granted (in dollars per share)	$ 61.45	$ 48.45	$ 53.40
Number of Options
Granted (in shares)			15,165
Non-vested stock options
Granted (in shares)			15,165
Restricted stock grants and performance stock units
Compensation expenses
Total unrecognized compensation cost				$ 9,200,000
Unrecognized compensation cost recognized over a weighted average period (in years)	1 month 21 days
Employee stock options
Share-Based Compensation
Options outstanding (in shares)	57,653	300,580	458,103	57,653	60,231
Compensation expenses
Period from grant date after which stock options become exercisable, minimum (in months)	6 months
Period from grant date within which incentive stock options are exercisable, maximum (in years)	7 years
Number of Options
Outstanding at the beginning of the period (in shares)	60,231	300,580	458,103
Exercised (in shares)	(2,578)	(232,514)	(157,523)
Cancelled (in shares)		(7,835)
Outstanding at the end of the period (in shares)	57,653	60,231	300,580
Exercisable (in shares)				57,653	60,231
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 14.74	$ 13.70	$ 13.73
Exercised (in dollars per share)	14.78	13.36	13.80
Cancelled (in dollars per share)		15.86
Outstanding at the end of the period (in dollars per share)	$ 14.74	$ 14.74	$ 13.70
Exercisable (in dollars per share)				$ 14.74	$ 14.74
Weighted Average Remaining Contractual Term
Outstanding, Weighted Average Remaining Contractual Term (in years)	2 years 1 month 6 days	3 years 1 month 6 days
Exercisable, Weighted Average Remaining Contractual Term (in years)	2 years 1 month 6 days	3 years 1 month 6 days
Aggregate Intrinsic Value
Average intrinsic value of shares outstanding				$ 1,474,500	$ 3,005,100
Average intrinsic value of shares exercisable				$ 1,474,500	$ 3,005,100
Total intrinsic value of options exercised	$ 100,000	$ 10,500,000	$ 7,100,000
Performance stock units
Share-Based Compensation
Granted (in shares)	69,132	87,864	90,264
Granted (in dollars per share)	$ 61.45	$ 48.81	$ 53.41
Performance period	3 years
Number of shares
Nonvested sharess at the beginning of the period (in shares)	233,571	370,917	468,576
Granted (in shares)	69,132	87,864	90,264
Additional shares awarded from the 2015 grant	83,042	67,853	92,335
Vested (in shares)	(166,084)	(203,582)	(277,029)
Cancelled (in shares)	(23,052)	(89,481)	(3,229)
Nonvested shares at the end of the period (in shares)	196,609	233,571	370,917
Weighted Average Grant-Date Fair Value
Nonvested shares at the beginning of the period (in dollars per share)	$ 45.44	$ 30.84	$ 19.70
Granted (in dollars per share)	61.45	48.81	53.41
Additional shares awarded from the 2015 grant (in dollars per share)	35.81	14.80	13.62
Vested (in dollars per share)	35.81	14.80	13.62
Cancelled (in dollars per share)	53.66	34.70	30.09
Nonvested shares at the end of the period (in dollars per share)	$ 54.17	$ 45.44	$ 30.84
Performance stock units | Maximum
Share-Based Compensation
Award percentage	200.00%	200.00%	200.00%
Performance stock units | Minimum
Share-Based Compensation
Award percentage	0.00%	0.00%	0.00%
Restricted stock units
Share-Based Compensation
Granted (in shares)	82,505	104,120	115,044
Granted (in dollars per share)	$ 61.45	$ 48.65	$ 53.40
Number of shares
Nonvested sharess at the beginning of the period (in shares)	284,686	575,781	815,590
Granted (in shares)	82,505	104,120	115,044
Vested (in shares)	(103,231)	(251,853)	(330,580)
Cancelled (in shares)	(25,983)	(143,362)	(24,273)
Nonvested shares at the end of the period (in shares)	237,977	284,686	575,781
Weighted Average Grant-Date Fair Value
Nonvested shares at the beginning of the period (in dollars per share)	$ 45.21	$ 27.71	$ 18.35
Granted (in dollars per share)	61.45	48.65	53.40
Vested (in dollars per share)	35.81	14.79	13.57
Cancelled (in dollars per share)	52.31	30.85	27.77
Nonvested shares at the end of the period (in dollars per share)	$ 54.15	$ 45.21	$ 27.71
Long Term Incentive Plan 2010
Share-Based Compensation
Number of shares authorized						4,500,000
Shares remaining available for future issuance				4,100,000
Long Term Incentive Plan 2010 | Restricted stock units
Share-Based Compensation
Vesting period	3 years
Granted (in dollars per share)	$ 61.45
Weighted Average Grant-Date Fair Value
Granted (in dollars per share)	$ 61.45
Long Term Incentive Plan 2010 | Restricted stock units | Director
Share-Based Compensation
Granted (in shares)	82,505
Number of shares
Granted (in shares)	82,505

Capital Transactions - Informat

Capital Transactions - Information About Stock Options Outstanding (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Options Exercisable
Borrowed amount	$ 3,236,002,000	$ 3,017,523,000
Employee stock options | $13.00 to $13.99
Stock options, exercise price
Exercise price range, low end of range (in dollars per share)	$ 13
Exercise price range, high end of range (in dollars per share)	$ 13.99
Options Outstanding
Number of options outstanding (in shares)	2,034
Options outstanding, Weighted Average Remaining Contractual Life	1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 13.51
Options Exercisable
Number of options Exercisable (in shares)	2,034
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 13.51
Employee stock options | $14.00 to $15.00
Stock options, exercise price
Exercise price range, low end of range (in dollars per share)	14
Exercise price range, high end of range (in dollars per share)	$ 15
Options Outstanding
Number of options outstanding (in shares)	55,619
Options outstanding, Weighted Average Remaining Contractual Life	1 year 1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 14.78
Options Exercisable
Number of options Exercisable (in shares)	55,619
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 14.78
Employee stock options | $13.00 to $15.00
Stock options, exercise price
Exercise price range, low end of range (in dollars per share)	13
Exercise price range, high end of range (in dollars per share)	$ 15
Options Outstanding
Number of options outstanding (in shares)	57,653
Options outstanding, Weighted Average Remaining Contractual Life	1 year 1 month 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 14.74
Options Exercisable
Number of options Exercisable (in shares)	57,653
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 14.74
PSP agreement | Warrant Shares
Options Exercisable
Warrants to purchase shares	370,720
Warrants exercise price	$ 28.38
Warrant term	5 years
Weighted average fair value of the warrants	$ 13.57
Secured loan
Options Exercisable
Warrants to purchase shares	211,416
Warrants exercise price	$ 28.38
Warrant term	5 years
Weighted average fair value of the warrants	$ 15.22
Borrowed amount	$ 60,000,000

Retirement Plans and Employee_3

Retirement Plans and Employee Stock Purchase Plans - Retirement Plans (Details) - SkyWest Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Plans
Required age for an employee to be eligible to participate in plan	18 years
Percentage of employer matching contribution based on length of service	100.00%
Minimum benefit plan percentage of participants compensation eligible for employer matching contribution based on position and years of service	2.00%
Maximum benefit plan percentage of participants compensation eligible for employer matching contribution based on position and years of service	12.00%
Company's combined contributions	$ 31.9	$ 40.7	$ 35.6

Retirement Plans and Employee_4

Retirement Plans and Employee Stock Purchase Plans - Employee Stock Purchase Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Stock Purchase Plans
Service period required to be completed for an employee to be eligible to participate in plan, minimum	90 days
Ownership interest in Company common stock to disqualify employee from participation in plan, maximum (as a percent)	5.00%
Maximum percentage of base salary which can be contributed by the employees	15.00%
Maximum amount of base salary which can be contributed annually by the employees	$ 25,000
Discount rate at which common stock can be purchased by the plan participant (as a percent)	5.00%
Summary of purchases made under the 2010 and 1995 Employee Stock Purchase Plans
Number of shares purchased	65,512	65,148	60,950
Average price of shares purchased (in dollars per share)	$ 42.45	$ 48.58	$ 49.85
2009 Stock Purchase Plan
Summary of purchases made under the 2010 and 1995 Employee Stock Purchase Plans
Stock based compensation expense	$ 0	$ 0	$ 0

Stock Repurchase (Details)

Stock Repurchase (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Repurchase
Common stock authorized for repurchase, maximum (in shares)	250
Common stock remaining number of shares authorized to repurchase	139.6
Common stock repurchased (in shares)	0.4	1.7	1
Common stock repurchased, value	$ 20	$ 94.6	$ 54.4
Weighted average price per share of common stock (in dollars per share)	$ 51.87	$ 56.86	$ 56.25
Payment of income tax obligation on employee equity awards	$ 6.2	$ 9.3	$ 13.6

Related-Party Transactions (Det

Related-Party Transactions (Details)	12 Months Ended
	Dec. 31, 2020USD ($)
Affiliated entity
Related Party Transactions
Purchase from related party	$ 223,050

Gain on Sale of ExpressJet (Det

Gain on Sale of ExpressJet (Details) - USD ($) $ in Thousands	Jan. 22, 2019	Jan. 11, 2019	Mar. 31, 2019	Dec. 31, 2019
Gain on sale	$ 46,500		$ 46,500	$ 46,525
Interest rate (as a percent)	6.85%
Asset Purchase Agreement | ExpressJet
Proceeds from sale of equipment		$ 60,800
Stock Purchase Agreement | ExpressJet
Cash received from stock sale	$ 18,800
Amount loaned to Kair Enterprises, Inc	$ 26,000

Investment in Other Companies (

Investment in Other Companies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)engine
Number of spare engines sold to Aero Engines | engine	15
Aero Engines, LLC.
Payments to acquire interest in joint venture	$ 22,300
Investment ownership (as a percent)	75.00%
Number of spare engines purchased | engine	15
Long-term debt	$ 0
Investment balance in Aero Engines	25,500
Additional interest in Joint venture	1,000
Company's portion of income generated by Aero Engines	$ 1,600

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 15, 2021	Dec. 31, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Common stock, par value (in dollars per share)		$ 0	$ 0
Subsequent event | Promissory Note | Until Fifth Anniversary of Closing Date
Subsequent Event [Line Items]
Interest rate (as a percent)	1.00%
Subsequent event | Promissory Note | Thereafter until the tenth anniversary of the Closing Date
Subsequent Event [Line Items]
Interest rate (as a percent)	2.00%
Subsequent event | Payroll Support Program Extension Agreement
Subsequent Event [Line Items]
Amount borrowed	$ 233.1
Subsequent event | Warrant Agreement
Subsequent Event [Line Items]
Warrants exercise price	$ 40.41
Minimum | Subsequent event | Promissory Note
Subsequent Event [Line Items]
Interest rate (as a percent)	0.00%
Maximum | Subsequent event | Promissory Note
Subsequent Event [Line Items]
Amount borrowed	$ 39.9
Maximum | Subsequent event | Warrant Agreement
Subsequent Event [Line Items]
Warrants to purchase shares	98,815

Quarterly Financial Data (Una_3

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 22, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data (Unaudited)
Operating revenues		$ 589,638	$ 457,493	$ 350,039	$ 729,936	$ 743,591	$ 760,295	$ 744,383	$ 723,694	$ 2,127,106	$ 2,971,963	$ 3,221,679
Operating income		(27,669)	74,553	(4,403)	66,321	125,305	146,441	144,093	96,419	108,802	512,258	474,280
Net income		$ (46,450)	$ 33,662	$ (25,715)	$ 29,988	$ 72,527	$ 91,339	$ 88,052	$ 88,181	$ (8,515)	$ 340,099	$ 280,372
Net income per common share:
Basic (in dollars per share)		$ (0.93)	$ 0.67	$ (0.51)	$ 0.60	$ 1.44	$ 1.80	$ 1.72	$ 1.71	$ (0.17)	$ 6.68	$ 5.40
Diluted (in dollars per share)		$ (0.93)	$ 0.66	$ (0.51)	$ 0.59	$ 1.43	$ 1.79	$ 1.71	$ 1.69	$ (0.17)	$ 6.62	$ 5.30
Weighted average common shares:
Basic (in shares)		50,181,000	50,181,000	50,140,000	50,277,000	50,395,000	50,746,000	51,145,000	51,440,000	50,195,000	50,932,000	51,914,000
Diluted (in shares)		50,181,000	50,622,000	50,140,000	50,559,000	50,796,000	51,129,000	51,477,000	52,098,000	50,195,000	51,375,000	52,871,000
Gain on sale of subsidiary	$ 46,500								$ 46,500		$ 46,525
Special items									$ 21,900		$ 21,869

SCHEDULE II -VALUATION AND QUAL

SCHEDULE II -VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Year	$ 15,908	$ 22,299	$ 17,255
Additions Charged to Costs and Expenses			5,044
Deductions		(6,391)
Balance at End of Year		15,908	22,299
Accounting Standards Update 2016-13
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Year	31,296
Additions Charged to Costs and Expenses	34,623
Deductions	(18)
Balance at End of Year	65,901	31,296
Allowance for inventory obsolescence
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Year	15,890	22,141	17,098
Additions Charged to Costs and Expenses	3,786		5,043
Deductions		(6,251)
Balance at End of Year	19,676	15,890	22,141
Allowance for doubtful accounts receivable
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Year	18	158	157
Additions Charged to Costs and Expenses			1
Deductions	(18)	(140)
Balance at End of Year		18	$ 158
Allowance for doubtful accounts receivable | Accounting Standards Update 2016-13
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of Year	15,388
Additions Charged to Costs and Expenses	30,837
Balance at End of Year	$ 46,225	$ 15,388