Allegiant Travel (ALGT) 10-K 29 Feb 24 2023 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2023	Feb. 01, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-33166
Entity Registrant Name	Allegiant Travel Co
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	20-4745737
Entity Address, Address Line One	1201 North Town Center Drive
Entity Address, City or Town	Las Vegas,
Entity Address, State or Province	NV
Entity Address, Postal Zip Code	89144
City Area Code	702
Local Phone Number	851-7300
Title of 12(b) Security	Common Stock, $0.001 Par Value
Trading Symbol	ALGT
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 Emerging Growth Company	false
Entity Small Business	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 1.9
Entity Common Stock, Shares Outstanding		18,286,324
Documents Incorporated by Reference	Portions of the Proxy Statement to be used in connection with the solicitation of proxies to be voted at the registrant’s annual meeting to be held on June 26, 2024, and to be filed with the Commission subsequent to the date hereof, are incorporated by reference into Part III of this Report on Form 10-K.
Entity Central Index Key	0001362468
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Audit Information [Abstract]
Auditor Name	KPMG LLP
Auditor Location	Dallas, TX
Auditor Firm ID	185

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 143,259	$ 229,989
Restricted cash	16,325	15,457
Short-term investments	671,414	725,063
Accounts receivable	70,743	106,578
Expendable parts, supplies and fuel, net of reserve of $10,284 and $8,079	36,335	35,546
Prepaid expenses and other current assets	63,054	161,636
TOTAL CURRENT ASSETS	1,001,130	1,274,269
Property and equipment (including $129,646 and $80,591 from VIEs, Note 6), net of accumulated depreciation of $964,866 and $814,837	3,447,111	2,810,693
Long-term investments	56,004	63,318
Deferred major maintenance, net of accumulated amortization of $143,275 and $108,779	165,767	157,410
Operating lease right-of-use assets, net	100,707	111,679
Deposits and other assets	98,691	93,928
TOTAL ASSETS:	4,869,410	4,511,297
CURRENT LIABILITIES
Accounts payable	54,484	58,335
Accrued liabilities	305,078	226,276
Current operating lease liabilities	20,873	19,973
Air traffic liability	353,488	379,459
Current loyalty program liability	38,447	32,888
Current maturities of long-term debt and finance lease obligations (including $22,627 and $9,315 from VIEs, Note 6), net of related costs of $8,038 and $6,599	439,937	152,900
TOTAL CURRENT LIABILITIES	1,212,307	869,831
LONG-TERM DEBT AND OTHER NONCURRENT LIABILITIES
Long-term debt and finance lease obligations (including $107,737 and $69,812 from VIEs, Note 6), net of current maturities and related costs of $14,477 and $16,866	1,819,717	1,944,078
Deferred income taxes	384,602	346,388
Noncurrent operating lease liabilities	82,410	94,972
Noncurrent loyalty program liability	32,366	23,612
Other noncurrent liabilities	9,448	11,718
TOTAL LIABILITIES:	3,540,850	3,290,599
SHAREHOLDERS' EQUITY
Common stock, par value $0.001, 100,000,000 shares authorized; 25,501,823 and 25,086,278 shares issued; 18,269,090 and 18,128,182 shares outstanding in 2023 and 2022 respectively	26	25
Treasury shares, at cost, 7,232,733 and 6,958,096 shares in 2023 and 2022, respectively	(681,932)	(660,023)
Additional paid in capital	741,055	709,471
Accumulated other comprehensive income, net	3,991	1,257
Retained earnings	1,265,420	1,169,968
TOTAL EQUITY:	1,328,560	1,220,698
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY:	$ 4,869,410	$ 4,511,297

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Expendable parts, supplies and fuel, reserve	$ 10,284	$ 8,079
Property, plant and equipment, net	3,447,111	2,810,693
Property, plant, and equipment, owned, accumulated depreciation	964,866	814,837
Accumulated amortization of other deferred costs	143,275	108,779
Long-term debt and lease obligation, current	439,937	152,900
Debt issuance costs, gross, current	8,038	6,599
Long-term debt and lease obligation	1,819,717	1,944,078
Debt issuance cost, gross, noncurrent	$ 14,477	$ 16,866
Treasury stock, common, shares (in shares)	7,232,733	6,958,096
Expendable parts, supplies and fuel, net of reserve of $10,284 and $8,079	$ 36,335	$ 35,546
Accounts receivable	$ 70,743	$ 106,578
Common Stock
Common stock, par or stated value per share (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares, issued (in shares)	25,501,823	25,086,278
Common stock, shares, outstanding (in shares)	18,269,090	18,128,182
Variable Interest Entity, Primary Beneficiary [Member]
Property, plant and equipment, net	$ 129,646	$ 80,591
Long-term debt and lease obligation, current	22,627	9,315
Long-term debt and lease obligation	$ 107,737	$ 69,812

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING REVENUES:
Passenger	$ 2,324,397	$ 2,137,762	$ 1,578,436
Third party products	112,579	100,959	86,487
Fixed fee contracts	68,548	60,937	41,184
Other	4,333	2,171	1,803
Total operating revenues	2,509,857	2,301,829	1,707,910
OPERATING EXPENSES:
Aircraft fuel	695,871	814,803	440,235
Salaries and benefits	687,803	552,413	484,573
Station operations	256,560	255,168	243,346
Depreciation and amortization	223,130	197,542	181,035
Maintenance and repairs	123,802	117,814	105,943
Sales and marketing	114,616	100,678	72,742
Aircraft lease rentals	24,948	23,621	21,242
Other	133,501	113,532	83,902
Payroll Support Programs grant recognition	0	0	(202,181)
Special charges, net of recoveries	28,645	34,612	13,998
Total operating expenses	2,288,876	2,210,183	1,444,835
OPERATING INCOME	220,981	91,646	263,075
OTHER (INCOME) EXPENSES:
Interest income	(46,615)	(16,469)	(1,814)
Interest expense	153,186	115,711	68,474
Capitalized interest	(45,132)	(12,640)	0
Other, net	491	91	(205)
Total other expenses	61,930	86,693	66,455
INCOME BEFORE INCOME TAXES	159,051	4,953	196,620
INCOME TAX PROVISION	41,455	2,460	44,767
NET INCOME	$ 117,596	$ 2,493	$ 151,853
Earnings per share to common shareholders:
Basic (in dollars per share)	$ 6.32	$ 0.14	$ 8.69
Diluted (in dollars per share)	$ 6.29	$ 0.14	$ 8.68
Shares used for computation:
Basic (in shares)	17,945	17,959	17,212
Diluted (in shares)	18,019	18,034	17,231
Cash dividends declared per share (in dollars per share)	$ 1.20	$ 0	$ 0

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 117,596	$ 2,493	$ 151,853
Other comprehensive income:
Change in available for sale securities, net of tax	2,734	(799)	2,083
TOTAL COMPREHENSIVE INCOME	$ 120,330	$ 1,694	$ 153,936

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock	Parent
Common stock, shares, outstanding (in shares)		16,405,000
Common Stock, Value, Issued		$ 23
TOTAL EQUITY	$ 699,363		$ 329,753	$ (27)	$ 1,015,622	$ (646,008)
Exercises of stock options and stock-settled SARs (Shares)		113,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition			27,058				$ 27,058
Stock Repurchased During Period, Shares		1,553,000
Treasury Stock, Value, Acquired, Cost Method		$ 2	335,137				335,139
Total number of shares purchased in year	39,760	40,000
Stock Issued During Period, Value, Employee Stock Purchase Plan						7,951	7,951
Other Comprehensive Income (Loss), Net of Tax				2,083
Unrealized gain on short-term investments, net of tax							2,083
Adjustments to Additional Paid in Capital, Warrant Issued			105				105
Net Income	$ 151,853				151,853		151,853
Cash dividends (per Share)	$ 0
Common stock, shares, outstanding (in shares)		18,111,000
Common Stock, Value, Issued		$ 25
TOTAL EQUITY	$ 1,223,552		692,053	2,056	1,167,475	(638,057)
Exercises of stock options and stock-settled SARs (Shares)		323,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition			17,418				17,418
Stock Repurchased During Period, Shares		(379,000)
Treasury Stock, Value, Acquired, Cost Method						(29,905)	(29,905)
Total number of shares purchased in year	73,268	73,000
Stock Issued During Period, Value, Employee Stock Purchase Plan						7,939	7,939
Other Comprehensive Income (Loss), Net of Tax				(799)
Unrealized gain on short-term investments, net of tax							(799)
Net Income	$ 2,493				2,493		2,493
Cash dividends (per Share)	$ 0
Common stock, shares, outstanding (in shares)		18,128,000
Common Stock, Value, Issued	$ 25	$ 25
TOTAL EQUITY	$ 1,220,698		709,471	1,257	1,169,968	(660,023)
Exercises of stock options and stock-settled SARs (Shares)		415,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition		$ 1	31,584				31,585
Stock Repurchased During Period, Shares		(374,000)
Treasury Stock, Value, Acquired, Cost Method						(30,076)	(30,076)
Total number of shares purchased in year	99,802	100,000
Stock Issued During Period, Value, Employee Stock Purchase Plan						8,167	8,167
Other Comprehensive Income (Loss), Net of Tax				2,734
Unrealized gain on short-term investments, net of tax							2,734
Net Income	$ 117,596				117,596		$ 117,596
Cash dividends (per Share)	$ 1.20
Common stock, shares, outstanding (in shares)		18,269,000
Common Stock, Value, Issued	$ 26	$ 26
TOTAL EQUITY	$ 1,328,560		$ 741,055	$ 3,991	$ 1,265,420	$ (681,932)

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Stockholders' Equity [Abstract]
Cash dividends (per Share)	$ 1.20	$ 0	$ 0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING ACTIVITIES:
Net income	$ 117,596	$ 2,493	$ 151,853
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	223,130	197,542	181,035
(Gain) loss on aircraft and other equipment disposals	920	2,158	(3,052)
Special charges, net of recoveries	27,189	34,268	13,998
Share-based compensation expense	29,749	15,198	16,127
Deferred income taxes	38,214	2,178	43,761
Other adjustments	(11,284)	12,082	14,777
Changes in certain assets and liabilities:
Accounts receivable	29,390	(33,887)	(14,717)
Tax receivable	3,932	3,697	143,624
Prepaid expenses	(1,825)	(10,625)	(4,026)
Accounts payable	(5,031)	14,770	10,402
Accrued liabilities	79,881	58,309	48,060
Air traffic liability	(25,971)	72,006	(55)
Deferred major maintenance	(67,862)	(54,675)	(59,747)
Other assets/liabilities	(14,936)	(12,464)	(3,847)
Net cash provided by operating activities	423,092	303,050	538,193
INVESTING ACTIVITIES:
Purchase of investment securities	(890,880)	(1,267,266)	(1,248,575)
Proceeds from maturities of investment securities	976,804	1,301,286	954,970
Aircraft pre-delivery deposits	(342,167)	(96,532)	(11,924)
Purchase of property and equipment, including capitalized interest	(528,320)	(434,690)	(243,613)
Purchase of note receivable	0	0	(50,000)
Insurance proceeds from damage to property & equipment	35,730	5,450	98
Other investing activities	26,956	328	5,766
Net cash used in investing activities	(721,877)	(491,424)	(593,278)
FINANCING ACTIVITIES:
Proceeds from issuance of common stock	0	0	335,139
Cash dividends paid to shareholders	(22,144)	0	0
Proceeds from the issuance of debt and finance lease obligations	642,581	863,627	281,657
Repurchase of common stock	(30,078)	(29,905)	0
Principal payments on debt and finance lease obligations	(480,818)	(701,596)	(301,096)
Debt issuance costs	(7,116)	(14,297)	(8,287)
Sunseeker construction financing disbursements (deposits)	102,330	(92,650)	(30,000)
Other financing activities	8,168	7,940	8,054
Net cash provided by financing activities	212,923	33,119	285,467
NET CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(85,862)	(155,255)	230,382
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT BEGINNING OF PERIOD	245,446	400,701	170,319
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH AT END OF PERIOD	159,584	245,446	400,701
CASH PAYMENTS/(RECEIPTS) FOR:
Interest paid, net of amount capitalized	111,912	82,903	43,511
Income tax paid (refunds)	1,012	308	(128,540)
SUPPLEMENTAL DISCLOSURE OF NONCASH TRANSACTIONS
Right-of-use (ROU) assets acquired	8,320	0	33,260
Purchases of property and equipment in accrued liabilities	71,672	54,641	17,671
Flight equipment acquired under finance leases	$ 0	$ 192,457	$ 101,340

Organization and Business of Co

Organization and Business of Company (Notes)	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business of Company	Organization and Business of Company Allegiant Travel Company (the “Company”) is a leisure travel company focused on providing travel services and products to residents of under-served cities in the United States. The Company operates a low-cost, low utilization passenger airline which sells air transportation both on a stand-alone basis and bundled with the sale of ancillary air-related and third party services and products. The Company also provides air transportation under fixed fee flying arrangements, generates other ancillary revenues, and owns and operates the Sunseeker Resort and Aileron, the related golf course. Scheduled service and fixed fee air transportation services have similar operating margins, economic characteristics, and production processes (check-in, baggage handling and flight services) which target the same class of customers, and are subject to the same regulatory environment. As a result, the Company believes its airline activities operate under one reportable segment and does not separately track expenses for scheduled service and fixed fee air transportation services. The Company's Sunseeker Resort represents a separate reportable segment. Refer to Note 14 for additional information.

Special Charges

Special Charges	12 Months Ended
	Dec. 31, 2023
Unusual or Infrequent Items, or Both [Abstract]
Special Charges	Special Charges As a result of Hurricane Ian's direct hit on the southwest coast of Florida on September 28, 2022, the construction site of Sunseeker Resort at Charlotte Harbor (the "Resort" or "Sunseeker Resort") was damaged. Additionally in the fourth quarter of 2022, there was another weather-related event and a fire that caused additional damage. Based on the Company’s assessment of these damages and the anticipated future restoration costs, an estimated loss of $52.1 million was recorded as a special charge in 2022, which was offset by $18.1 million of recorded insurance recoveries during 2022. In 2023, an additional $2.4 million of loss was recorded as a result of updated damage assessments by the Company and the insurance providers. During third quarter 2023, the Sunseeker Resort construction site incurred additional damages related to Hurricane Idalia. Based on the Company’s assessment of these damages and the anticipated future restoration costs, an estimated loss of $23.6 million was recorded as a special charge in 2023. The estimate is preliminary and subject to change as the damage assessment by the Company and the insurance providers continues. During the years ended December 31, 2023 and December 31, 2022, the Company recorded losses of $26.0 million and $52.1 million, respectively, which were offset by $32.5 million and $18.1 million of insurance recoveries, respectively. To date, the Company has recorded insurance recoveries of $1.0 million and $49.5 million, respectively, related to the 2023 and 2022 hurricanes and related weather events. The Company anticipates that additional insurance recoveries related to the losses incurred in 2023 and 2022 will be recorded in future periods. Due to the heavy maintenance needs on certain aging Airbus airframes and capacity constraints at the Company's maintenance, repair, and overhaul contractors, the Company reevaluated its fleet plan and identified 21 airframes for early retirement to coincide with 737 MAX aircraft deliveries as scheduled under an amendment to the Company's agreement with The Boeing Company signed in September 2023. Two airframes were fully retired in 2023 and the remaining airframes are scheduled to be retired between January 2024 and September 2025. The accelerated depreciation on these airframes resulting from a change in the estimated useful life is recorded as a special charge of $35.1 million for the year ended December 31, 2023. Special charges in 2021 were incurred due to the impacts of the COVID-19 pandemic. The charges were related to accelerated depreciation on aircraft identified for early retirement, impairment loss on a building related to a discontinued business unit, and acceleration of certain stock awards. A portion of the special charge recorded in 2022 relates to accelerated depreciation on the last of the COVID-19 aircraft identified for early retirement, which amount is separate from the $35.1 million described above. Special Charges The table below summarizes special charges recorded during the years ended December 31, 2023, 2022, and 2021. Year Ended December 31, (in thousands) 2023 2022 2021 Sunseeker weather and related events $ 26,045 $ 52,095 $ — Sunseeker weather and related events, insurance recoveries (1) (32,491) (18,050) — Accelerated depreciation on airframes identified for early retirement 35,091 567 2,521 COVID-19 and related charges — — 11,477 Total special charges $ 28,645 $ 34,612 $ 13,998 (1) Includes $8.3 million of business interruption insurance proceeds for the year ended December 31, 2023. No business interruption insurance recoveries were received for the years ended December 31, 2022 or December 31, 2021.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements include the accounts of Allegiant Travel Company and its majority-owned operating subsidiaries. The Company's investments in unconsolidated affiliates, which are 50 percent or less owned, are accounted for under the equity or cost method. All intercompany balances and transactions have been eliminated. The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results could differ from these estimates. The Company has reclassified certain prior period amounts to conform to the current period presentation . Cash and Cash Equivalents Cash and cash equivalents include highly liquid investments and interest bearing instruments with original maturities of three months or less when purchased. Such investments are carried at cost which approximates fair value. Restricted Cash Restricted cash represents escrowed funds under fixed fee contracts, and cash collateral held against letters of credit required by hotel properties for guaranteed room availability, airports and certain other parties. Accounts Receivable Accounts receivable are recorded at invoiced amount which approximates fair value. In addition to income tax receivables, the accounts receivable consist primarily of amounts due from credit card companies associated with the sale of tickets for future travel. These receivables are short-term and generally settle within a few days of sale. There are also receivables related to commission amounts due from Enterprise Holdings Inc. based on terms in the rental car provider agreement and amounts due related to fixed fee charter agreements. If deemed necessary, the Company records charges to its allowance for doubtful accounts for amounts not expected to be collected, for which the balance was immaterial for all years presented. Short-term and Long-term Investments The Company’s investments in marketable securities are classified as available-for-sale and are reported at fair value with the net unrealized gain or (loss) reported as a component of accumulated other comprehensive income (loss) in shareholders’ equity. For investments in an unrealized loss position, the Company determines whether a credit loss exists by considering information about the collectability of the instrument and current market conditions. There have been no credit losses in the years presented. Investment securities with original maturities of three months or less are classified as cash equivalents. Investment securities with original maturities greater than three months are classified as either short-term investments or long-term investments based on the maturity date in relation to the balance sheet date. Short-term investments have a maturity date less than or equal to one year from the balance sheet date, and long-term investments have a maturity date greater than one year from the balance sheet date. The amortized cost of investment securities sold is determined by the specific identification method with any realized gains or losses reflected in other (income) expense. The Company had minimal realized losses during the years ended December 31, 2023, 2022, and 2021. The Company believes unrealized losses related to debt securities are not other-than-temporary and does not intend to sell these securities prior to amortized cost recoverability. The Company attempts to minimize its concentration risk with regard to its cash, cash equivalents, and investment portfolio. This is accomplished by diversifying and limiting amounts among different counterparties, the type of investment, and the amount invested in any individual security, commercial paper, or money market fund. Expendable Parts, Supplies and Fuel, Net Expendable parts, supplies and fuel inventories are valued at cost using the first-in, first-out method. Such expendable parts, supplies and fuel are charged to expense as they are used in operations. An obsolescence allowance for expendable parts and supplies is based on salvage values and the average remaining useful life of the fleet. The obsolescence allowance for expendable parts and supplies was $10.3 million and $8.1 million at December 31, 2023 and 2022, respectively. Deposits and Other Assets Deposits and Other Assets consist primarily of airport deposits, aircraft lease deposits, deposits as required by the construction loan agreement for the Sunseeker Resort and a note receivable from the counter-party in the Company’s joint venture alliance. The Company also had outstanding receivables from third parties as of December 31, 2023 and 2022, of which $17.0 million and $18.3 million respectively, was due more than one year after the balance sheet date. Operating Lease Right-of-Use Asset and Liability The Company determines if an arrangement is a lease at inception and has lease agreements for aircraft, office facilities, office equipment, certain airport and terminal facilities, and other space and assets with non-cancelable lease terms. Certain real estate and property leases, aircraft leases, and various other operating leases are measured on the balance sheet with a lease liability and right-of-use ("ROU") asset. Airport terminal leases mostly include variable lease payments outside of those based on a fixed index, and are therefore excluded from consideration. ROU assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the obligation to make scheduled lease payments. ROU assets and liabilities are recognized on the lease commencement date based on the present value of lease payments over the lease term. At lease commencement, the present value of lease payments is calculated using the rate implicit in the lease, if known, or an estimated incremental borrowing rate which takes into consideration recent debt issuances as well as other applicable market data available. Lease payments include fixed payments, variable payments based on an index or rate, reasonably certain purchase options, termination penalties, and others as required by the Accounting Standards (ASU) 2016-02, Leases (Topic 842). Lease payments do not include variable lease payments other than those that depend on an index or rate, any guarantee by the lessee of the lessor’s debt, or any amount allocated to non-lease components. Lease terms include options to extend when it is reasonably certain that the option will be exercised. Leases with a term of 12 months or less are not recorded on the balance sheet. Additionally, lease and non-lease components are accounted for as a single lease component for real estate agreements. Property and Equipment Property and equipment are recorded at cost and depreciated using the straight-line method over their estimated useful lives less any estimated salvage value. Property under finance leases and related obligations are initially recorded at an amount equal to the present value of future minimum lease payments computed using the rate implicit in the lease, if known, or on the basis of the Company’s estimated incremental borrowing rate, and depreciation is recorded on a straight-line basis and is included within depreciation and amortization expense. The estimated useful lives of the principal asset classes are shown below. Aircraft, engines and related rotable parts 10 - 25 Years Buildings and leasehold improvements 10 - 39 Years Equipment 3 - 10 Years Computer hardware and software 3 - 15 Years In estimating the useful lives and residual values of aircraft, the Company primarily relies upon actual experience with the same or similar aircraft types, current and projected future market information, and input from other industry sources. Subsequent revisions to these estimates could be caused by changing market prices of the Company’s aircraft, changes in utilization of the aircraft, and other fleet events. Changes in the estimate for useful lives or residual values of the Company’s property and equipment could result in changes in depreciation expense. The Company is required to make pre-delivery payments ("PDPs") towards the purchase price of new aircraft and engines prior to delivery. These deposits are included in flight equipment on the Company's consolidated balance sheets. Interest is capitalized by applying a capitalization rate to the weighted-average carrying amount of expenditures for qualifying assets over the period and depreciated over the estimated useful life of the related asset(s) acquired/developed. Software Capitalization The Company capitalizes certain internal and external costs related to the acquisition and development of computer software during the application development stage of projects. The Company amortizes these capitalized costs using the straight-line method over the estimated useful life of the software, which typically ranges from three Aircraft Maintenance and Repair Costs The Company accounts for all non-major maintenance and repair costs incurred for its fleet under the direct expense method. Under this method, maintenance and repair costs for aircraft are charged to maintenance and repair expenses as incurred. Maintenance and repair costs include all parts, materials, and line maintenance activities required to maintain the Company's fleet. The Company accounts for major maintenance costs of its airframes and engines using the deferral method. Under this method, the Company capitalizes the cost of major maintenance events, which are amortized as a component of depreciation and amortization expense, over the estimated period until the next scheduled major maintenance event. During 2023 and 2022, the Company capitalized $68.5 million and $60.6 million of major maintenance costs. Amortization expense related to major maintenance costs was $55.5 million, $43.8 million, and $42.1 million for the years ended December 31, 2023, 2022, and 2021 respectively. Measurement of Impairment of Long-Lived Assets The Company records impairment losses on long-lived assets used in operations, consisting principally of property and equipment, when events or changes in circumstances indicate, in management’s judgment, that the assets might be impaired, and the undiscounted future cash flows estimated to be generated by those assets are less than the carrying amount of those assets. In making these determinations, the Company utilizes certain assumptions, including, but not limited to: (i) estimated fair value of the assets; and (ii) estimated future cash flows expected to be generated by these assets, which are based on additional assumptions such as asset utilization, length of service for which the asset will be used in operations, and estimated salvage values. The Company did not recognize any impairment for the years ended December 31, 2023 and December 31, 2022. Revenue Recognition Passenger revenue Passenger revenue includes scheduled service revenue, ancillary air-related charges, and travel point redemptions from the co-brand Allegiant credit card and the Company's non-card loyalty program. Revenue from travel point redemptions from the co-brand credit card and the loyalty program are described in the Allways Rewards ® Credit Card Program and Allways Rewards ® Loyalty Program sections below. Scheduled service revenue consists of ticket revenue generated from nonstop flights in the Company’s route network, recognized either when the transportation is provided, or when ticket voucher breakage occurs. Nonrefundable scheduled itineraries expire on the date of the intended flight, unless the date is extended by notification from the customer in advance. Itineraries sold for transportation not yet used, as well as unexpired vouchers, are included in air traffic liability. Ancillary air-related charges include various services and products related to the flight such as baggage fees, the use of the Company’s website to purchase scheduled service transportation, advance seat assignments, and other services which are not included in the base ticket price. Revenues from air-related charges are recognized when the transportation is provided. If a customer cancels a flight, a voucher may be issued for a future flight, at which time the associated revenue is recognized in scheduled service revenue upon completion of the future flight. Additionally, the Company estimates the value of vouchers that will expire unused and recognizes such revenue at the time of issuance. Various taxes and fees, assessed on the sale of tickets to customers, are collected by the Company serving as an agent, and remitted to taxing authorities. These taxes and fees are not included as revenue in the Company’s consolidated statements of income and are recorded as a liability until remitted to the appropriate taxing authority. Third party products revenue Ancillary third party products revenue is generated from the sale of hotel rooms, rental cars and ticket attractions, as well as marketing revenue associated with the co-brand credit card. Revenue from the sale of third party products is recognized at the time the product is utilized, such as the time a purchased hotel room is occupied. Revenue from the sale of third party products is recorded net of amounts paid to wholesale providers, travel agent commissions, and transaction costs. Revenue from travel point redemptions from the co-brand credit card and the loyalty program are described in the Allways Rewards ® Credit Card Program and Allways Rewards ® Loyalty Program sections below. Fixed fee contract revenue Fixed fee contract revenue consists of fees under agreements to provide charter service on a year-round and ad hoc basis. Fixed fee contract revenue is recognized when the transportation is provided. Sunseeker Resort Sunseeker Resort's revenue from contracts with customers primarily consists of sales of rooms, food and beverage, golf, retail and other goods and services. As compensation for such goods and services, the Company is typically entitled to a fixed nightly fee for an agreed upon period and additional fixed fees for any ancillary services purchased. These fees are generally payable at the time the hotel guest checks out of the hotel. The Company generally satisfies the performance obligations over time, and the Company recognizes the revenue from room sales and from other ancillary guest services on a daily basis, as the rooms are occupied and the Company has rendered the services. Sunseeker Resort revenues are included in other revenue in the consolidated statements of income. Allways Rewards® Credit Card Program Under the Allegiant co-brand credit card arrangement, points are sold and consideration is received under an agreement with the issuer bank that expires in 2031. Under this arrangement, the Company identified the following deliverables: travel points to be awarded (the travel component), use of the Company’s brand and access to its member lists, and certain other advertising and marketing elements (collectively the marketing component). Each of these deliverables is accounted for separately and allocation of the consideration from the agreement is determined based on the relative selling price of each deliverable. The Company applied a level of management judgment and estimation in determining the best estimate of selling price for each deliverable by considering multiple inputs and methods including, but not limited to, the redemption value of points awarded, discounted cash flows, brand value, volume discounts, published selling prices, number of points to be awarded and number of points expected to be redeemed. Revenue from the travel component is deferred based on its relative selling price and is recognized into passenger revenue when the points are redeemed by cardholders and the underlying service is provided. Revenue from the marketing component is considered earned in the period in which points are sold and is therefore recognized into third party products revenue in the same period. Allways Rewards® Loyalty Program Allegiant’s Allways Rewards® Loyalty Program enables program members to earn points for every dollar they spend on the Company’s website. Under the program, which launched in August 2021, members continue to accumulate points until the time they decide to redeem them. In addition to opportunities to redeem points for flights, lodging, rental cars, and at the Sunseeker Resort, the program leverages Allegiant's partnerships to offer additional rewards to members, including sports tickets and exclusive experiences. Members can also earn points by using their Allegiant co-brand credit card. Under Allways Rewards®, members receive one point for every dollar spent at Allegiant.com, and two points per $1 for spending over $500 (excluding taxes and fees). The Company utilizes the deferred revenue method of accounting for points earned through the program based on the stand-alone selling price and revenue is recognized when points are redeemed and the underlying service has been provided. The stand-alone selling price of points is adjusted for an estimate of points that will not be redeemed (“breakage”) using a statistical model based on historical redemption patterns to develop an estimate of the likelihood of future redemption. Advertising Costs Advertising costs are charged to expense in the period incurred. Advertising expense was $41.0 million, $40.1 million and $31.3 million for the years ended December 31, 2023, 2022 and 2021, respectively. Preopening expenses Preopening expenses represent personnel, advertising, and other costs incurred prior to the opening of Sunseeker Resort and are expensed as incurred. During the year ended December 31, 2023, the Company incurred $26.5 million of preopening expenses related to the opening of the Resort, which is included in salaries and benefits expense, sales and marketing expense, and other expense in the consolidated statements of income. Earnings per Share Basic and diluted earnings per share are computed using the two-class method. Under the two-class method, the Company attributes net income to two classes, common stock and unvested restricted stock awards. Unvested restricted stock awards granted to employees under the Company’s Long-Term Incentive Plan are considered participating securities because they receive non-forfeitable rights to cash dividends at the same rate as common stock. Diluted net income per share is calculated using the more dilutive of two methods. Under both methods, the exercise of employee stock options is assumed using the treasury stock method. The assumption of vesting of restricted stock, however, differs as described below: 1. Assume vesting of restricted stock using the treasury stock method. 2. Assume unvested restricted stock awards are not vested, and allocate earnings to common shares and unvested restricted stock awards using the two-class method. For the years ended December 31, 2023, 2022 and 2021, the second method above was used in the computation because it was more dilutive than the first method. The following table sets forth the computation of net income per share on a basic and diluted basis for the periods indicated: Year ended December 31, (in thousands, except per share data) 2023 2022 2021 Basic: Net income $ 117,596 $ 2,493 $ 151,853 Less income allocated to participating securities (4,188) (32) (2,218) Net income attributable to common stock $ 113,408 $ 2,461 $ 149,635 Earnings per share, basic $ 6.32 $ 0.14 $ 8.69 Weighted-average shares outstanding 17,945 17,959 17,212 Diluted: Net income $ 117,596 $ 2,493 $ 151,853 Less income allocated to participating securities (4,175) (32) (2,215) Net income attributable to common stock $ 113,421 $ 2,461 $ 149,638 Earnings per share, diluted $ 6.29 $ 0.14 $ 8.68 Weighted-average shares outstanding 17,945 17,959 17,212 Dilutive effect of stock options and restricted stock 249 132 145 Adjusted weighted-average shares outstanding under treasury stock method 18,194 18,091 17,357 Participating securities excluded under two-class method (175) (57) (126) Adjusted weighted-average shares outstanding under two-class method 18,019 18,034 17,231 Stock awards outstanding of 81,748, 79,644, and 815 shares (not in thousands) as of December 31, 2023, 2022, and 2021, respectively, were excluded from the computation of diluted earnings per share as they were antidilutive. Share-Based Compensation The Company accounts for share-based compensation in accordance with accounting standards which require the compensation cost related to share-based payment transactions be recognized in the Company’s consolidated statements of income. The share-based compensation cost is measured based on grant date fair value. The Company’s share-based employee compensation plan is more fully discussed in Not e 12 . Income Taxes The Company recognizes deferred income taxes based on the asset and liability method required by accounting standards. Deferred tax assets and liabilities are determined based on the timing differences between book basis for financial reporting purposes and tax basis of the assets and liabilities and measured using the enacted tax rates and provisions of the enacted tax law. A valuation allowance for deferred tax assets is recorded if it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company determines the net non-current deferred tax assets or liabilities separately for federal, state, foreign and other local jurisdictions. The Company’s income tax returns are subject to examination by the Internal Revenue Service (“IRS”) and other tax authorities in the jurisdictions where the Company operates. The Company assesses potentially unfavorable outcomes of such examinations based on the criteria set forth in uncertain tax position accounting standards. The accounting standards prescribe a minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. Accounting standards for income taxes utilize a two-step approach for evaluating tax positions. Recognition (Step I) occurs when the Company concludes that a tax position, based on its technical merits, is more likely than not to be sustained upon examination. Measurement (Step II) is only addressed if the position is deemed to be more likely than not to be sustained. Under Step II, the tax benefit is measured as the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement. The tax positions failing to qualify for initial recognition are recognized in the first subsequent interim period they meet the “more likely than not” standard. If it is subsequently determined that a previously recognized tax position no longer meets the “more likely than not” standard, it is required that the tax position be derecognized. As applicable, the Company will recognize accrued penalties and interest related to unrecognized tax benefits in the provision for income taxes. Recent Accounting Pronouncements In October 2023, the Financial Standards Accounting Board (FASB) issued Accounting Standards Update (ASU) 2023-06, Disclosure Improvements to align the requirements in the FASB Accounting Standards Codification with the SEC's regulations in response to the SEC's August 2018 final rule that updated and simplified certain disclosure requirements. Each amendment in the ASU will only be effective on the date the related disclosures are removed from Regulation S-X or Regulation S-K by the SEC, and will no longer be effective if the SEC has not removed the applicable disclosure requirement by June 30, 2027. Early adoption is prohibited. The Company is currently evaluating the potential impact that the standard will have on its financial statement disclosures. In November 2023, the FASB issued ASU 2023-07 "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures," which expands annual and interim disclosure requirements for reportable segments, primarily through enhanced disclosures about significant segment expenses. ASU 2023-07 is effective for the Company's annual periods beginning January 1, 2024, and for interim periods beginning January 1, 2025, with early adoption permitted. The Company is currently evaluating the potential effect that the updated standard will have on its financial statement disclosures. In December 2023, the FASB issued ASU 2023-09 "Income Taxes (Topics 740): Improvements to Income Tax Disclosures." The new standard requires expanded income tax disclosure of specific categories in the rate reconciliation and income taxes paid, disaggregated by jurisdiction. ASU 2023-09 is effective for the Company's annual periods beginning January 1, 2025, with early adoption and retrospective application permitted. The Company is currently evaluating the potential effect that the updated standard will have on its financial statement disclosures.

Revenue Recognition

Revenue Recognition	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition Passenger revenue Passenger revenue is the most significant category in the Company's reported operating revenues, as outlined below: Year Ended December 31, (in thousands) 2023 2022 2021 Scheduled service $ 1,133,001 $ 1,062,753 $ 769,371 Ancillary air-related charges 1,137,226 1,025,549 788,064 Loyalty redemptions 54,170 49,460 21,001 Total passenger revenue $ 2,324,397 $ 2,137,762 $ 1,578,436 Sales of passenger tickets not yet flown are recorded in air traffic liability. Passenger revenue is recognized when transportation is provided. As of December 31, 2023, the air traffic liability balance was $353.5 million, of which approximately $303.6 million was related to forward bookings, with the remaining $49.9 million related to credit vouchers for future travel. The normal contract term of passenger tickets is 12 months and passenger revenue associated with future travel will principally be recognized within this time frame. Of the $379.5 million that was recorded in the air traffic liability balance at December 31, 2022, substantially all was recognized into passenger revenue during the 12 months ended December 31, 2023. In 2020, the Company announced that credit vouchers issued for canceled travel beginning in January 2020 would have an extended expiration date of two years from the original booking date. This policy continued for credit vouchers issued through June 30, 2021. Estimates of passenger revenue to be recognized from air traffic liability for credit voucher breakage during this period may be subject to variability and differ from historical experience due to the change in contract duration and uncertainty regarding demand for future air travel. Effective July 1, 2021, vouchers issued have an expiration date of one year from the original booking date. The Company periodically evaluates the estimated amount of credit vouchers expected to expire unused and any adjustment is removed from air traffic liability and included in passenger revenue in the period in which the evaluation is complete. Loyalty redemptions The following table presents the activity of the co-brand credit card and the loyalty program as of the dates indicated: Year Ended December 31, (in thousands) 2023 2022 Balance at January 1 $ 56,500 $ 40,449 Points awarded 68,483 65,511 Points redeemed (54,170) (49,460) Balance at December 31 $ 70,813 $ 56,500 The current portion of the loyalty program liability represents the estimate of revenue to be recognized in the next 12 months based on historical trends, with the remaining balance reflected in other noncurrent liabilities and expected to be recognized into revenue in periods thereafter.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consisted of the following: As of December 31, (in thousands) 2023 2022 Airline Flight equipment $ 3,346,216 $ 2,937,767 Computer hardware and software 274,927 209,808 Land and buildings/leasehold improvements 63,863 62,227 Other property and equipment 109,727 95,156 Sunseeker Resort Land and buildings/leasehold improvements 559,112 — Other property and equipment 53,743 — Construction in progress 4,389 320,572 Total property and equipment 4,411,977 3,625,530 Less accumulated depreciation and amortization (964,866) (814,837) Property and equipment, net $ 3,447,111 $ 2,810,693 As of December 31, 2023, the Company had firm commitments to purchase 51 aircraft which are expected to be delivered between 2024 and 2026.

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consisted of the following: As of December 31, (in thousands) 2023 2022 Fixed-rate debt and finance lease obligations due through 2032 $ 1,834,754 $ 1,720,998 Variable-rate debt due through 2029 424,900 375,980 Total long-term debt and finance lease obligations, net of related costs 2,259,654 2,096,978 Less current maturities, net of related costs 439,937 152,900 Long-term debt and finance lease obligations, net of current maturities and related costs $ 1,819,717 $ 1,944,078 Weighted average fixed-interest rate on debt 6.3 % 6.5 % Weighted average variable-interest rate on debt 7.9 % 6.1 % Interest Rate(s) Per Annum at As of December 31, (in thousands) Maturity Dates December 31, 2023 2023 2022 Senior secured notes 2027 7.25% $ 550,000 $ 700,000 Consolidated variable interest entities 2024 — 2029 2.92 % — 5.19% 130,650 79,453 Revolving credit facilities 2024 — 2027 7.97% 200,000 30,327 Debt secured by aircraft, engines, other equipment and real estate 2025 — 2031 1.87 % — 8.26% 596,271 466,335 Finance leases 2028 — 2032 4.44 % — 7.01% 455,248 494,328 Construction loan agreement 2028 5.75% 350,000 350,000 Total debt $ 2,282,169 $ 2,120,443 Related costs (22,515) (23,465) Total debt net of related costs $ 2,259,654 $ 2,096,978 Maturities of long-term debt as of December 31, 2023, for the next five years and thereafter, in the aggregate, are: (in thousands) As of December 31, 2023 2024 (1) 439,937 2025 180,611 2026 176,152 2027 709,354 2028 328,569 Thereafter 425,031 Total debt and finance lease obligations, net of related costs $ 2,259,654 Senior Secured Notes In August, 2022, the Company issued $550.0 million in aggregate principal amount of its 7.250% Senior Secured Notes due 2027 (the “2027 Notes”) pursuant to an Indenture, dated as of August 17, 2022. The 2027 Notes are secured by first priority security interests in, subject to permitted liens, substantially all of the property and assets of the Company and its subsidiaries (other than Sunseeker Resort and its subsidiaries), except that the collateral package excludes aircraft, aircraft engines, real property and certain other assets. The collateral also secures the Company’s $75.0 million revolving credit facility (described below), on a pari passu basis. The 2027 Notes bear interest at a fixed rate of 7.25 percent per annum, payable in cash on February 15 and August 15 of each year. The 2027 Notes will mature on August 15, 2027. The 2027 Notes contain certain covenants that limit the ability of the Company to, among other things: (i) make restricted payments; (ii) incur indebtedness or issue preferred stock; (iii) create or incur certain liens; (iv) dispose of loyalty program or brand intellectual property collateral; (v) merge, consolidate or sell all or substantially all assets and (vi) enter into certain transactions with affiliates. The 2027 Notes also require the Company to comply with certain affirmative covenants, including to maintain a minimum aggregate amount of liquidity of $300.0 million. If the Company fails to satisfy the minimum liquidity requirement, then the Company will be required to pay additional interest on all outstanding 2027 Notes in an amount equal to 2.0% per annum of the principal amount of such 2027 Notes until the Company demonstrates compliance with the liquidity requirement. In November 2023, the Company prepaid the entirety of the $150.0 million outstanding on its 8.500% Senior Secured Notes issued in October 2020 and originally due February 2024. Consolidated Variable Interest Entities The Company evaluates ownership, contractual lease arrangements and other interests in entities to determine if they are variable interest entities ("VIEs") based on the nature and extent of those interests. The Company consolidates a VIE when, among other criteria, it has the power to direct the activities that most significantly impact the VIE’s economic performance as well as the obligation to absorb losses or the right to receive benefits of the VIE, thus making the Company the primary beneficiary of the VIE. During 2023, the Company, through a wholly owned subsidiary, entered into similarly structured agreements with trusts to borrow $63.0 million collateralized by aircraft and engines. The trusts were funded at inception. The borrowings bear interest at fixed rates and are payable in monthly installments through October 2028 and February 2029, at which time the Company will have purchase options at fixed amounts. As these transactions are common control transactions, the Company, as the primary beneficiary, has measured and recorded the assets and liabilities at their carrying values, which were $51.6 million and $63.0 million respectively, at the time of borrowing. Revolving Credit Facilities In August 2022, the Company entered into a credit agreement under which the Company is entitled to borrow up to $100.0 million. In October 2023, the Company extended the term of this agreement to August 2025 with all other terms to remain the same. The borrowing ability of the facility is based on the value of aircraft and engines placed into the collateral pool. The notes under the facility will bear interest at a floating rate based on SOFR. As of December 31, 2023, the facility remains undrawn. In August 2022, the Company entered into a credit agreement that provides a senior secured revolving loan facility of $75.0 million. The facility is secured by the same collateral that secures the 2027 Notes, has a term of 57 months and notes under the facility bear interest at a floating rate based on SOFR. As of December 31, 2023, the facility remains undrawn. In September 2022, the Company entered into a credit agreement under which the Company is entitled to borrow up to $200.0 million. The revolving credit facility has a term of 24 months and the borrowing ability is based on the amount of pre-delivery deposits paid on certain 737 MAX aircraft, the purchase rights for which the Company may choose to place in the collateral pool. The facility is secured by the purchase rights for the applicable aircraft. Any notes under the facility bear interest at a floating rate based on SOFR and all borrowings are due no later than December 31, 2024 or upon delivery of the applicable aircraft. As of December 31, 2023, the Company has fully drawn all $200.0 million under this facility. In March 2021, the Company entered into a revolving credit facility, under which it is entitled to borrow up to $50.0 million. In February, 2023, the Company extended the term of this agreement to March 2026 and upsized the capacity to $100.0 million. The borrowing ability is based on the value of the aircraft and engines placed into the collateral pool. The notes for amounts borrowed under the facility will bear interest at a floating rate based on SOFR. As of December 31, 2023, the facility remains undrawn. Other Secured Debt The Company is party to financing agreements under which aircraft, other equipment or other assets serve as collateral. Below are described those debt transactions entered into during 2023. In November 2023, the Company entered into a pre-delivery deposit financing facility to borrow up to $158.0 million secured by the Company's purchase rights for certain Boeing 737 MAX aircraft. The facility bears a floating interest rate based on SOFR and is due upon delivery of each aircraft or no later than June 30, 2025. As of December 31, 2023, the Company has drawn $113.9 million under the facility. In September 2023, the Company entered into a credit agreement under which the Company is entitled to borrow up to $412.1 million. In September 2023, the Company received funding of $196.4 million under the facility, which is collateralized by aircraft. The proceeds were used in part to pay off existing debt collateralized by aircraft. The outstanding balance bears interest at a fixed rate, to be paid in quarterly installments of principal and interest, and matures in September 2031. The remaining undrawn balance of the facility will be funded upon delivery of, and collateralized by, Boeing 737 MAX aircraft currently on order from Boeing. Future draws collateralized by 737 MAX aircraft will bear interest at a rate determined at the time of drawdown and will have a term of twelve years. In May 2023, the Company borrowed $92.7 million under a loan agreement secured by aircraft. The notes bear interest at a fixed rate, payable in quarterly installments maturing in May 2028. During the year ended December 31, 2023, the Company made a total of $207.8 million in payments to extinguish six variable rate facilities secured by aircraft. Construction Loan Agreement In October 2021, Sunseeker Florida, Inc. (“SFI”), a wholly-owned subsidiary of the Company, entered into a Credit Agreement pursuant to which SFI borrowed $350.0 million to fund the remaining construction of the initial phases of Sunseeker Resort. The loan is secured by the Resort. All of the shares in SFI are also pledged to secure the loan. The loan bears interest at 5.75 percent per annum payable semi-annually, provides for semi-annual principal payments of $26.0 million beginning in 2025 and matures in October 2028. The credit agreement includes covenants similar to the covenants in the Company’s 2027 Notes. To support the credit, the Company has guaranteed the full amount of the debt. As of December 31, 2023, the entirety of the borrowed funds have been released from the construction disbursement account. Finance Leases The Company has finance lease obligations related to 23 aircraft, which impacted the Company's recognized assets and liabilities as of December 31, 2023. See Note 7 for more information on finance lease obligations.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	Leases The Company had 23 aircraft under finance leases and 17 aircraft under operating leases as of December 31, 2023 with remaining terms through 2032. Lease Costs The components of lease costs recognized on the statements of income were as follows: Year Ended December 31, (in thousands) Classification on the Statements of Income 2023 2022 2021 Finance lease costs: Amortization of assets Depreciation and amortization $ 27,170 $ 17,579 $ 13,274 Interest on lease liabilities Interest expense 27,502 23,034 11,168 Operating lease cost Aircraft lease rentals; Station operations; Maintenance and repairs; Other operating expense 25,246 24,986 22,697 Variable lease cost Station operations; Maintenance and repairs; Other operating expense 1,563 1,469 2,565 Total lease cost $ 81,481 $ 67,068 $ 49,704 Lease position as of December 31, 2023 The table below presents the lease-related assets and liabilities recorded on the balance sheet. As of December 31, (in thousands) Classification on the Balance Sheet 2023 2022 Assets Operating lease assets Operating lease right-of-use assets, net $ 100,707 $ 111,679 Finance lease assets Property and equipment, net of accumulated depreciation 483,083 537,766 Total lease assets $ 583,790 $ 649,445 Liabilities Current Operating Current operating lease liabilities $ 20,873 $ 19,973 Finance Current maturities of long-term debt and finance lease obligations 25,352 39,080 Noncurrent Operating Noncurrent operating lease liabilities 82,410 94,972 Finance Long-term debt and finance lease obligations 429,896 455,248 Total lease liabilities $ 558,531 $ 609,273 Weighted-average remaining lease term Operating leases 7.4 years 7.0 years Finance leases 7.1 years 7.8 years Weighted-average discount rate Operating leases 5.5 % 5.4 % Finance leases 5.9 % 5.9 % Other Information The table below presents supplemental cash flow information related to leases during the years ended December 31, 2023 and 2022. Year Ended December 31, (in thousands) 2023 2022 2021 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows for operating leases $ 25,774 $ 25,775 $ 18,987 Operating cash flows for finance leases 27,672 22,366 10,697 Financing cash flows for finance leases 39,044 16,621 14,675 Maturities of Lease Liabilities The table below indicates the future minimum payments of lease liabilities as of December 31, 2023. (in thousands) Operating Leases Finance Leases 2024 $ 25,912 $ 51,408 2025 23,850 51,408 2026 13,896 51,108 2027 11,688 51,108 2028 9,997 65,908 Thereafter 42,616 336,168 Total lease payments 127,959 607,108 Less imputed interest (24,676) (151,860) Total lease obligations 103,283 455,248 Less current obligations (20,873) (25,352) Long-term lease obligations $ 82,410 $ 429,896

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	Shareholders’ Equity The Company is authorized by its board of directors to acquire the Company’s stock through open market purchases under its share repurchase program. As repurchase authority is exhausted, the board of directors has, to date, authorized additional expenditures for share repurchases. The Company suspended stock repurchases upon the onset of the pandemic and as part of accepting benefits from the U.S. Treasury under the Payroll Support Programs, the Company agreed not to repurchase stock through September 30, 2022. The Company recommenced repurchasing shares in the fourth quarter 2022 after those restrictions expired. Share repurchases consisted of the following during the periods indicated: Year Ended December 31, 2023 2022 2021 Shares repurchased (1) 309,155 377,529 — Average price per share $ 78.61 $ 78.94 $ — Total (in thousands) $ 24,303 $ 29,802 $ — (1) Share amounts shown above include only open market repurchases and do not include shares withheld from employees for tax withholding obligations related to restricted stock vestings, which were 65,284, 1,423, and zero shares (not in thousands) for 2023, 2022, and 2021 respectively. Cash dividends declared by the Board and paid by the Company consisted of the following during the periods indicated: Year Ended December 31, 2023 2022 2021 Total quarterly cash dividends declared, per share $ 1.20 $ — $ — Total cash dividends paid (in thousands) 22,144 — — The Company suspended payment of cash dividends upon the onset of the pandemic, and as part of accepting benefits from the U.S. Treasury under the Payroll Support Programs, the Company agreed not to pay cash dividends through September 30, 2022. The Company recommenced payment of cash dividends in the second half of 2023.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Investments The Company measures certain financial assets and liabilities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Accounting standards pertaining to fair value measurements establish a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1 - Defined as observable inputs such as quoted prices in active markets for identical assets or liabilities Level 2 - Defined as inputs other than Level 1 inputs that are either directly or indirectly observable Level 3 - Defined as unobservable inputs for which little or no market data exists, therefore requiring an entity to develop its own assumptions The Company uses the market approach valuation technique to determine fair value for investment securities. The assets classified as Level 1 consist of money market funds for which original cost approximates fair value. The assets classified as Level 2 consist of commercial paper, municipal debt securities, federal agency debt securities, U.S. treasury bonds and corporate debt securities, which are valued using quoted market prices or alternative pricing sources including transactions involving identical or comparable assets and models utilizing market observable inputs. The Company has no investment securities classified as Level 3. For those assets classified as Level 2 that are not in active markets, the Company obtains fair value from pricing sources using quoted market prices for identical or comparable instruments, and uses pricing models which include all significant observable inputs: maturity dates, issue dates, settlement dates, benchmark yields, reported trades, broker-dealer quotes, issue spreads, benchmark securities, bids, offers and other market related data. These inputs are observable or can be derived from, or corroborated by, observable market data for substantially the full term of the asset. Financial instruments measured at fair value on a recurring basis: As of December 31, 2023 As of December 31, 2022 (in thousands) Total Level 1 Level 2 Total Level 1 Level 2 Cash equivalents Money market funds $ 33,613 $ 33,613 $ — $ 88,073 $ 88,073 $ — Commercial paper 19,575 — 19,575 50,791 — 50,791 Municipal debt securities 7,848 — 7,848 8,599 — 8,599 Federal agency debt securities 8,201 — 8,201 — — — US Treasury bonds 2,000 — 2,000 — — — Total cash equivalents 71,237 33,613 37,624 147,463 88,073 59,390 Short-term Commercial paper 237,870 — 237,870 421,279 — 421,279 Corporate debt securities 210,982 — 210,982 166,136 — 166,136 Federal agency debt securities 194,522 — 194,522 107,222 — 107,222 US Treasury Bonds 14,126 — 14,126 — — — Municipal debt securities 13,914 — 13,914 30,426 — 30,426 Total short-term 671,414 — 671,414 725,063 — 725,063 Long-term Corporate debt securities 43,869 — 43,869 35,688 — 35,688 Federal agency debt securities 12,135 — 12,135 20,050 — 20,050 Municipal debt securities — — — 7,580 — 7,580 Total long-term 56,004 — 56,004 63,318 — 63,318 Total financial instruments $ 798,655 $ 33,613 $ 765,042 $ 935,844 $ 88,073 $ 847,771 There were no significant transfers between Level 1 and Level 2 assets for the years ended December 31, 2023 or 2022. Long-term Debt None of the Company's long-term debt is publicly traded. The Company has determined the estimated fair value of all of this debt to be Level 3, as certain inputs used to determine the fair value of these agreements are unobservable and, therefore, could be sensitive to changes in inputs.The Company utilizes the discounted cash flow method to estimate the fair value of Level 3 debt. Carrying value and estimated fair value of long-term debt, including current maturities and without reduction for related costs: As of December 31, 2023 As of December 31, 2022 (in thousands) Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Fair Value Level Non-publicly held debt $ 1,826,921 $ 1,815,351 $ 1,626,114 $ 1,561,939 3 Other Due to the short term nature, carrying amounts of cash, cash equivalents, restricted cash, accounts receivable and accounts payable approximate fair value.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to income taxation in the United States and various state jurisdictions in which it operates. In accordance with income tax accounting standards, the Company recognizes tax benefits or expenses on the temporary differences between the financial reporting and tax bases of its assets and liabilities. The entirety of the Company's income before taxes are from its domestic operations. Income Tax Provision/(Benefit) The provision (benefit) for income taxes is composed of the following: Year ended December 31, (in thousands) 2023 2022 2021 Current: Federal $ — $ 6 $ (494) State 3,306 73 552 Foreign 204 209 (6) Total current 3,510 288 52 Deferred: Federal 36,910 1,189 40,693 State 1,035 983 4,022 Total deferred 37,945 2,172 44,715 Total income tax provision $ 41,455 $ 2,460 $ 44,767 Reconciliation of Effective Tax Rate The effective tax rate on income before income taxes differed from the federal statutory income tax rate as follows: Year ended December 31, (in thousands) 2023 2022 2021 Income tax expense at federal statutory rate $ 33,401 $ 1,040 $ 41,575 State income taxes, net of federal income tax benefit 3,503 1,189 4,257 Foreign income tax expense 204 210 (6) Executive compensation 3,692 57 2,359 Federal tax credits (2,034) (1,103) (385) Stock compensation 1,936 1,016 (2,058) Other 753 51 (975) Total income tax expense $ 41,455 $ 2,460 $ 44,767 Deferred Taxes The major components of the Company’s net deferred tax assets and liabilities are as follows: As of December 31, (in thousands) 2023 2022 Deferred tax assets: Employee benefits $ 8,410 $ 9,938 Net operating loss 22,237 30,370 Tax credits 4,128 4,290 Other (1) 30,576 18,644 Less: valuation allowance 1,214 1,214 Total deferred tax assets 64,137 62,028 Deferred tax liabilities: Prepaid expenses 4,516 4,223 Depreciation 434,620 399,622 Other 9,603 4,571 Total deferred tax liabilities 448,739 408,416 Net deferred tax liabilities $ 384,602 $ 346,388 (1) Other deferred tax assets consists of interest expense and research and development expenses. Net Operating Loss and Tax Credit Carryforwards

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsDuring the years ended December 31, 2023, 2022 and 2021, there were no related party transactions that required disclosure.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2023
Employee Benefit Plans [Abstract]
Employee Benefit Plans	Employee Benefit Plans 401(k) Plan The Company has a defined contribution plan covering all eligible employees. Under the plan, employees may contribute up to 90 percent of their eligible annual compensation with the Company making matching contributions on employee deferrals of up to 5 percent of eligible employee wages. The Company recognized expense under this plan of $25.5 million, $24.0 million, and $21.4 million for the years ended December 31, 2023, 2022 and 2021, respectively. Share-based employee compensation The Company reserved 2,000,000 shares of common stock for the Company to grant stock options, restricted stock, cash-settled stock appreciation rights ("SARs") and other stock-based awards to certain officers, directors and employees of the Company under the 2022 Long-Term Incentive Plan (the "2022 Plan"). The 2022 Plan is administered by the compensation committee of the board of directors. Employee Stock Purchase Plan The Company reserved 1,000,000 shares of common stock for employee purchases under the 2014 Employee Stock Purchase Plan ("ESPP"). Shares are purchased semi-annually, at a discount, based on the market value at period-end. Employees may contribute up to 25 percent of their base pay per offering period, not to exceed $25,000 each calendar year, for the purchase of common stock. The ESPP is a compensatory plan under applicable accounting guidance and results in the recognition of compensation expense. The following table provides information about the Company’s ESPP activity during 2023, 2022, and 2021: Year Ended Total number of shares purchased in year Average price paid per share Weighted-average fair value of discount under the ESPP (1) December 31, 2021 39,760 $ 174.68 $ 30.00 December 31, 2022 73,268 $ 97.85 $ 16.25 December 31, 2023 99,802 $ 85.27 $ 14.44 (1) The weighted-average fair value of the discount under the ESPP granted is equal to a percentage discount from the market value of the common stock at the end of each semi-annual purchase period. 15 percent is the maximum allowable discount under the ESPP. Compensation expense For the years ended December 31, 2023, 2022 and 2021, the Company recorded compensation expense of $31.5 million, $16.3 million and $17.2 million, respectively, related to restricted stock, stock options and the ESPP. Forfeiture rates are estimated at the time of grant based on historical actuals for similar grants and are matched to actuals over the vesting period. The unrecognized compensation cost was $39.7 million as of December 31, 2023 for unvested restricted stock expected to be recognized over a weighted-average period of 2.69 years. As of December 31, 2023, there was $0.1 million unrecognized compensation cost related to stock options. Restricted stock awards The closing price of the Company's stock on the date of grant is used as the fair value for the issuance of restricted stock. Most of the Company's unvested restricted stock awards, subject generally to the individual's continued employment or service, vest over a three year period or longer for certain of the Company's executive officers. A summary of the status of non-vested restricted stock grants during the y ears ended December 31, 2023, 2022 and 2021 is presented below: Shares Weighted Average Grant Date Fair Value Per Share Non-vested at December 31, 2020 265,527 $ 142.25 Granted 120,456 194.66 Vested (197,530) 136.71 Forfeited (6,900) 147.05 Non-vested at December 31, 2021 181,553 $ 183.63 Granted 374,540 89.31 Vested (74,170) 180.54 Forfeited (52,055) 123.01 Non-vested at December 31, 2022 429,868 $ 109.33 Granted 567,004 93.57 Vested (238,020) 119.00 Forfeited (151,459) 94.07 Non-vested at December 31, 2023 607,393 $ 94.64 The total grant date fair value of restricted stock that vested during the years ended December 31, 2023, 2022 and 2021 was $28.3 million, $13.4 million and $27.0 million, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company leases assets including aircraft, office facilities, office equipment, certain airport and terminal facilities, and other space. These commitments have remaining non-cancelable lease terms, which range from 2024 to 2048. Refer to Note 7 for more information on the Company's lease agreements. The Company's contractual purchase commitments consist primarily of aircraft and engine acquisitions. The total future commitments are as follows: (in thousands) As of December 31, 2023 2024 $ 866,545 2025 673,612 2026 159,679 Total purchase commitments $ 1,699,836 Aircraft Commitments As of December 31, 2023, the Company had entered into purchase agreements for 51 aircraft which are expected to deliver from 2024 through 2026. Contingencies The Company is party to collective bargaining agreements with the employee groups listed below. As of December 31, 2023, the percentage of full-time equivalent employees for each of these pay groups was as follows: As of December 31, 2023 Pilots 17.9 % Flight Attendants 23.4 Maintenance Technicians 11.2 Flight Dispatchers 0.9 Total 53.4 % See Item I - Business, for further discussion on the status of each group which has elected union representation. The Company is subject to certain other legal and administrative actions it considers routine to its business activities. The Company believes the ultimate outcome of any pending legal or administrative matters will not have a material adverse impact on its financial position, liquidity or results of operations.

Segments

Segments	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Segments	Segments Operating segments are components of a company for which separate financial and operating information is regularly evaluated and reported to the Chief Operating Decision Maker ("CODM"), and is used to allocate resources and analyze performance. The Company's CODM is the executive leadership team, which reviews information about the Company's two operating segments: Airline and Sunseeker Resort. Airline Segment The Airline segment operates as a single business unit and includes all scheduled service air transportation, ancillary air-related products and services, third party products and services, fixed fee contract air transportation and other airline-related revenue. The CODM evaluation includes, but is not limited to, route and flight profitability data, ancillary and third party product and service offering statistics, and fixed fee contract information when making resource allocation decisions with the goal of optimizing consolidated financial results. Sunseeker Resort Segment The Sunseeker Resort segment operates as a single business unit and includes hotel rooms and suites for occupancy, group meeting facilities, food and beverage options, the Aileron Golf Course and other Resort amenities. The Resort opened on December 15, 2023. The CODM evaluation includes, but is not limited to, demand for hospitality offerings, occupancy rates, room pricing, food and beverage offerings, other charge points at the Resort and competitive information when making resource allocations with the goal of optimizing consolidated financial results. For the year ended December 31, 2023, the Company recorded $26.5 million of preopening expenses related to the opening of the Resort, which is included in salaries and benefits expense, sales and marketing expense, and other expense in the consolidated statements of income. Selected information for the Company's segments and the reconciliation to the consolidated financial statement amounts are as follows: (in thousands) Airline Sunseeker Resort Consolidated Year Ended December 31, 2023 Operating revenue: Passenger $ 2,324,397 $ — $ 2,324,397 Third party products 112,579 — 112,579 Fixed fee contract 68,548 — 68,548 Other 1,444 2,889 4,333 Operating income (loss) 251,468 (30,487) 220,981 Interest income (46,615) — (46,615) Interest expense (1) 130,512 21,868 152,380 Capitalized interest (21,838) (23,294) (45,132) Depreciation and amortization 220,915 2,215 223,130 Capital expenditures 568,309 321,044 889,353 Year Ended December 31, 2022 Operating revenue: Passenger $ 2,137,762 $ — $ 2,137,762 Third party products 100,959 — 100,959 Fixed fee contract 60,937 — 60,937 Other 2,169 2 2,171 Operating income (loss) 136,968 (45,322) 91,646 Interest income (16,469) — (16,469) Interest expense (1) 92,785 16,046 108,831 Capitalized interest (4,308) (8,332) (12,640) Depreciation and amortization 197,433 109 197,542 Capital expenditures 475,254 288,408 763,662 Year Ended December 31, 2021 Operating revenue: Passenger $ 1,578,436 $ — $ 1,578,436 Third party products 86,487 — 86,487 Fixed fee contract 41,184 — 41,184 Other 1,803 — 1,803 Operating income (loss) 271,073 (7,998) 263,075 Interest income (1,814) — (1,814) Interest expense (1) 66,585 1,818 68,403 Depreciation and amortization 180,923 112 181,035 Capital expenditures 309,982 50,629 360,611 (1) Excludes losses on debt extinguishment. Total assets were as follows as of the dates indicated: (in thousands) As of December 31, 2023 As of December 31, 2022 Airline $ 4,213,288 $ 4,047,134 Sunseeker Resort 656,122 464,163 Consolidated $ 4,869,410 $ 4,511,297

Subsequent Events (Notes)

Subsequent Events (Notes)	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events

Summary of Significant Accoun_2

Summary of Significant Accounting Policies - (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation [Policy Text Block]	Basis of Presentation The accompanying consolidated financial statements include the accounts of Allegiant Travel Company and its majority-owned operating subsidiaries. The Company's investments in unconsolidated affiliates, which are 50 percent or less owned, are accounted for under the equity or cost method. All intercompany balances and transactions have been eliminated. The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results could differ from these estimates. The Company has reclassified certain prior period amounts to conform to the current period presentation
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents Cash and cash equivalents include highly liquid investments and interest bearing instruments with original maturities of three months or less when purchased. Such investments are carried at cost which approximates fair value.
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Restricted Cash
Receivable [Policy Text Block]	Accounts Receivable Accounts receivable are recorded at invoiced amount which approximates fair value. In addition to income tax receivables, the accounts receivable consist primarily of amounts due from credit card companies associated with the sale of tickets for future travel. These receivables are short-term and generally settle within a few days of sale. There are also receivables related to commission amounts due from Enterprise Holdings Inc. based on terms in the rental car provider agreement and amounts due related to fixed fee charter agreements. If deemed necessary, the Company records charges to its allowance for doubtful accounts for amounts not expected to be collected, for which the balance was immaterial for all years presented.
Marketable Securities, Policy [Policy Text Block]	Short-term and Long-term Investments The Company’s investments in marketable securities are classified as available-for-sale and are reported at fair value with the net unrealized gain or (loss) reported as a component of accumulated other comprehensive income (loss) in shareholders’ equity. For investments in an unrealized loss position, the Company determines whether a credit loss exists by considering information about the collectability of the instrument and current market conditions. There have been no credit losses in the years presented. Investment securities with original maturities of three months or less are classified as cash equivalents. Investment securities with original maturities greater than three months are classified as either short-term investments or long-term investments based on the maturity date in relation to the balance sheet date. Short-term investments have a maturity date less than or equal to one year from the balance sheet date, and long-term investments have a maturity date greater than one year from the balance sheet date. The amortized cost of investment securities sold is determined by the specific identification method with any realized gains or losses reflected in other (income) expense. The Company had minimal realized losses during the years ended December 31, 2023, 2022, and 2021. The Company believes unrealized losses related to debt securities are not other-than-temporary and does not intend to sell these securities prior to amortized cost recoverability. The Company attempts to minimize its concentration risk with regard to its cash, cash equivalents, and investment portfolio. This is accomplished by diversifying and limiting amounts among different counterparties, the type of investment, and the amount invested in any individual security, commercial paper, or money market fund.
Inventory, Policy [Policy Text Block]	Expendable Parts, Supplies and Fuel, Net Expendable parts, supplies and fuel inventories are valued at cost using the first-in, first-out method. Such expendable parts, supplies and fuel are charged to expense as they are used in operations. An obsolescence allowance for expendable parts and supplies is based on salvage values and the average remaining useful life of the fleet. The obsolescence allowance for expendable parts and supplies was $10.3 million and $8.1 million at December 31, 2023 and 2022, respectively.
Deposits and Other Assets	Deposits and Other Assets Deposits and Other Assets consist primarily of airport deposits, aircraft lease deposits, deposits as required by the construction loan agreement for the Sunseeker Resort and a note receivable from the counter-party in the Company’s joint venture alliance.
Lessee, Leases [Policy Text Block]	Operating Lease Right-of-Use Asset and Liability The Company determines if an arrangement is a lease at inception and has lease agreements for aircraft, office facilities, office equipment, certain airport and terminal facilities, and other space and assets with non-cancelable lease terms. Certain real estate and property leases, aircraft leases, and various other operating leases are measured on the balance sheet with a lease liability and right-of-use ("ROU") asset. Airport terminal leases mostly include variable lease payments outside of those based on a fixed index, and are therefore excluded from consideration. ROU assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the obligation to make scheduled lease payments. ROU assets and liabilities are recognized on the lease commencement date based on the present value of lease payments over the lease term. At lease commencement, the present value of lease payments is calculated using the rate implicit in the lease, if known, or an estimated incremental borrowing rate which takes into consideration recent debt issuances as well as other applicable market data available. Lease payments include fixed payments, variable payments based on an index or rate, reasonably certain purchase options, termination penalties, and others as required by the Accounting Standards (ASU) 2016-02, Leases (Topic 842). Lease payments do not include variable lease payments other than those that depend on an index or rate, any guarantee by the lessee of the lessor’s debt, or any amount allocated to non-lease components. Lease terms include options to extend when it is reasonably certain that the option will be exercised. Leases with a term of 12 months or less are not recorded on the balance sheet. Additionally, lease and non-lease components are accounted for as a single lease component for real estate agreements.
Property, Plant and Equipment, Policy [Policy Text Block]	Property and Equipment Property and equipment are recorded at cost and depreciated using the straight-line method over their estimated useful lives less any estimated salvage value. Property under finance leases and related obligations are initially recorded at an amount equal to the present value of future minimum lease payments computed using the rate implicit in the lease, if known, or on the basis of the Company’s estimated incremental borrowing rate, and depreciation is recorded on a straight-line basis and is included within depreciation and amortization expense. The estimated useful lives of the principal asset classes are shown below. Aircraft, engines and related rotable parts 10 - 25 Years Buildings and leasehold improvements 10 - 39 Years Equipment 3 - 10 Years Computer hardware and software 3 - 15 Years In estimating the useful lives and residual values of aircraft, the Company primarily relies upon actual experience with the same or similar aircraft types, current and projected future market information, and input from other industry sources. Subsequent revisions to these estimates could be caused by changing market prices of the Company’s aircraft, changes in utilization of the aircraft, and other fleet events. Changes in the estimate for useful lives or residual values of the Company’s property and equipment could result in changes in depreciation expense. The Company is required to make pre-delivery payments ("PDPs") towards the purchase price of new aircraft and engines prior to delivery. These deposits are included in flight equipment on the Company's consolidated balance sheets. Interest is capitalized by applying a capitalization rate to the weighted-average carrying amount of expenditures for qualifying assets over the period and depreciated over the estimated useful life of the related asset(s) acquired/developed.
Internal Use Software, Policy [Policy Text Block]	Software Capitalization The Company capitalizes certain internal and external costs related to the acquisition and development of computer software during the application development stage of projects. The Company amortizes these capitalized costs using the straight-line method over the estimated useful life of the software, which typically ranges from three
Aircraft Maintenance And Repair Costs	Aircraft Maintenance and Repair Costs The Company accounts for all non-major maintenance and repair costs incurred for its fleet under the direct expense method. Under this method, maintenance and repair costs for aircraft are charged to maintenance and repair expenses as incurred. Maintenance and repair costs include all parts, materials, and line maintenance activities required to maintain the Company's fleet.
Measurement of Impairment of Long-Lived Assets, Policy [Policy Text Block]	Measurement of Impairment of Long-Lived Assets The Company records impairment losses on long-lived assets used in operations, consisting principally of property and equipment, when events or changes in circumstances indicate, in management’s judgment, that the assets might be impaired, and the undiscounted future cash flows estimated to be generated by those assets are less than the carrying amount of those assets. In making these determinations, the Company utilizes certain assumptions, including, but not limited to: (i) estimated fair value of the assets; and (ii) estimated future cash flows expected to be generated by these assets, which are based on additional assumptions such as asset utilization, length of service for which the asset will be used in operations, and estimated salvage values.
Revenue [Policy Text Block]	Revenue Recognition Passenger revenue Passenger revenue includes scheduled service revenue, ancillary air-related charges, and travel point redemptions from the co-brand Allegiant credit card and the Company's non-card loyalty program. Revenue from travel point redemptions from the co-brand credit card and the loyalty program are described in the Allways Rewards ® Credit Card Program and Allways Rewards ® Loyalty Program sections below. Scheduled service revenue consists of ticket revenue generated from nonstop flights in the Company’s route network, recognized either when the transportation is provided, or when ticket voucher breakage occurs. Nonrefundable scheduled itineraries expire on the date of the intended flight, unless the date is extended by notification from the customer in advance. Itineraries sold for transportation not yet used, as well as unexpired vouchers, are included in air traffic liability. Ancillary air-related charges include various services and products related to the flight such as baggage fees, the use of the Company’s website to purchase scheduled service transportation, advance seat assignments, and other services which are not included in the base ticket price. Revenues from air-related charges are recognized when the transportation is provided. If a customer cancels a flight, a voucher may be issued for a future flight, at which time the associated revenue is recognized in scheduled service revenue upon completion of the future flight. Additionally, the Company estimates the value of vouchers that will expire unused and recognizes such revenue at the time of issuance. Various taxes and fees, assessed on the sale of tickets to customers, are collected by the Company serving as an agent, and remitted to taxing authorities. These taxes and fees are not included as revenue in the Company’s consolidated statements of income and are recorded as a liability until remitted to the appropriate taxing authority. Third party products revenue Ancillary third party products revenue is generated from the sale of hotel rooms, rental cars and ticket attractions, as well as marketing revenue associated with the co-brand credit card. Revenue from the sale of third party products is recognized at the time the product is utilized, such as the time a purchased hotel room is occupied. Revenue from the sale of third party products is recorded net of amounts paid to wholesale providers, travel agent commissions, and transaction costs. Revenue from travel point redemptions from the co-brand credit card and the loyalty program are described in the Allways Rewards ® Credit Card Program and Allways Rewards ® Loyalty Program sections below. Fixed fee contract revenue Fixed fee contract revenue consists of fees under agreements to provide charter service on a year-round and ad hoc basis. Fixed fee contract revenue is recognized when the transportation is provided. Sunseeker Resort Sunseeker Resort's revenue from contracts with customers primarily consists of sales of rooms, food and beverage, golf, retail and other goods and services. As compensation for such goods and services, the Company is typically entitled to a fixed nightly fee for an agreed upon period and additional fixed fees for any ancillary services purchased. These fees are generally payable at the time the hotel guest checks out of the hotel. The Company generally satisfies the performance obligations over time, and the Company recognizes the revenue from room sales and from other ancillary guest services on a daily basis, as the rooms are occupied and the Company has rendered the services. Sunseeker Resort revenues are included in other revenue in the consolidated statements of income. Allways Rewards® Credit Card Program Under the Allegiant co-brand credit card arrangement, points are sold and consideration is received under an agreement with the issuer bank that expires in 2031. Under this arrangement, the Company identified the following deliverables: travel points to be awarded (the travel component), use of the Company’s brand and access to its member lists, and certain other advertising and marketing elements (collectively the marketing component). Each of these deliverables is accounted for separately and allocation of the consideration from the agreement is determined based on the relative selling price of each deliverable. The Company applied a level of management judgment and estimation in determining the best estimate of selling price for each deliverable by considering multiple inputs and methods including, but not limited to, the redemption value of points awarded, discounted cash flows, brand value, volume discounts, published selling prices, number of points to be awarded and number of points expected to be redeemed. Revenue from the travel component is deferred based on its relative selling price and is recognized into passenger revenue when the points are redeemed by cardholders and the underlying service is provided. Revenue from the marketing component is considered earned in the period in which points are sold and is therefore recognized into third party products revenue in the same period. Allways Rewards® Loyalty Program Allegiant’s Allways Rewards® Loyalty Program enables program members to earn points for every dollar they spend on the Company’s website. Under the program, which launched in August 2021, members continue to accumulate points until the time they decide to redeem them. In addition to opportunities to redeem points for flights, lodging, rental cars, and at the Sunseeker Resort, the program leverages Allegiant's partnerships to offer additional rewards to members, including sports tickets and exclusive experiences. Members can also earn points by using their Allegiant co-brand credit card. Under Allways Rewards®, members receive one point for every dollar spent at Allegiant.com, and two points per $1 for spending over $500 (excluding taxes and fees). The Company utilizes the deferred revenue method of accounting for points earned through the program based on the stand-alone selling price and revenue is recognized when points are redeemed and the underlying service has been provided. The stand-alone selling price of points is adjusted for an estimate of points that will not be redeemed (“breakage”) using a statistical model based on historical redemption patterns to develop an estimate of the likelihood of future redemption.
Advertising Cost [Policy Text Block]	Advertising Costs
Preopening Expenses Policy	Preopening expenses Preopening expenses represent personnel, advertising, and other costs incurred prior to the opening of Sunseeker Resort and are expensed as incurred. During the year ended December 31, 2023, the Company incurred $26.5 million of preopening expenses related to the opening of the Resort, which is included in salaries and benefits expense, sales and marketing expense, and other expense in the consolidated statements of income.
Earnings Per Share, Policy [Policy Text Block]	Earnings per Share Basic and diluted earnings per share are computed using the two-class method. Under the two-class method, the Company attributes net income to two classes, common stock and unvested restricted stock awards. Unvested restricted stock awards granted to employees under the Company’s Long-Term Incentive Plan are considered participating securities because they receive non-forfeitable rights to cash dividends at the same rate as common stock. Diluted net income per share is calculated using the more dilutive of two methods. Under both methods, the exercise of employee stock options is assumed using the treasury stock method. The assumption of vesting of restricted stock, however, differs as described below: 1. Assume vesting of restricted stock using the treasury stock method. 2. Assume unvested restricted stock awards are not vested, and allocate earnings to common shares and unvested restricted stock awards using the two-class method. For the years ended December 31, 2023, 2022 and 2021, the second method above was used in the computation because it was more dilutive than the first method. The following table sets forth the computation of net income per share on a basic and diluted basis for the periods indicated: Year ended December 31, (in thousands, except per share data) 2023 2022 2021 Basic: Net income $ 117,596 $ 2,493 $ 151,853 Less income allocated to participating securities (4,188) (32) (2,218) Net income attributable to common stock $ 113,408 $ 2,461 $ 149,635 Earnings per share, basic $ 6.32 $ 0.14 $ 8.69 Weighted-average shares outstanding 17,945 17,959 17,212 Diluted: Net income $ 117,596 $ 2,493 $ 151,853 Less income allocated to participating securities (4,175) (32) (2,215) Net income attributable to common stock $ 113,421 $ 2,461 $ 149,638 Earnings per share, diluted $ 6.29 $ 0.14 $ 8.68 Weighted-average shares outstanding 17,945 17,959 17,212 Dilutive effect of stock options and restricted stock 249 132 145 Adjusted weighted-average shares outstanding under treasury stock method 18,194 18,091 17,357 Participating securities excluded under two-class method (175) (57) (126) Adjusted weighted-average shares outstanding under two-class method 18,019 18,034 17,231 Stock awards outstanding of 81,748, 79,644, and 815 shares (not in thousands) as of December 31, 2023, 2022, and 2021, respectively, were excluded from the computation of diluted earnings per share as they were antidilutive.
Share-based Payment Arrangement [Policy Text Block]	Share-Based Compensation The Company accounts for share-based compensation in accordance with accounting standards which require the compensation cost related to share-based payment transactions be recognized in the Company’s consolidated statements of income. The share-based compensation cost is measured based on grant date fair value. The Company’s share-based employee compensation plan is more fully discussed in Not e 12 .
Income Tax, Policy [Policy Text Block]	Income Taxes The Company recognizes deferred income taxes based on the asset and liability method required by accounting standards. Deferred tax assets and liabilities are determined based on the timing differences between book basis for financial reporting purposes and tax basis of the assets and liabilities and measured using the enacted tax rates and provisions of the enacted tax law. A valuation allowance for deferred tax assets is recorded if it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company determines the net non-current deferred tax assets or liabilities separately for federal, state, foreign and other local jurisdictions. The Company’s income tax returns are subject to examination by the Internal Revenue Service (“IRS”) and other tax authorities in the jurisdictions where the Company operates. The Company assesses potentially unfavorable outcomes of such examinations based on the criteria set forth in uncertain tax position accounting standards. The accounting standards prescribe a minimum recognition threshold a tax position is required to meet before being recognized in the financial statements. Accounting standards for income taxes utilize a two-step approach for evaluating tax positions. Recognition (Step I) occurs when the Company concludes that a tax position, based on its technical merits, is more likely than not to be sustained upon examination. Measurement (Step II) is only addressed if the position is deemed to be more likely than not to be sustained. Under Step II, the tax benefit is measured as the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements In October 2023, the Financial Standards Accounting Board (FASB) issued Accounting Standards Update (ASU) 2023-06, Disclosure Improvements to align the requirements in the FASB Accounting Standards Codification with the SEC's regulations in response to the SEC's August 2018 final rule that updated and simplified certain disclosure requirements. Each amendment in the ASU will only be effective on the date the related disclosures are removed from Regulation S-X or Regulation S-K by the SEC, and will no longer be effective if the SEC has not removed the applicable disclosure requirement by June 30, 2027. Early adoption is prohibited. The Company is currently evaluating the potential impact that the standard will have on its financial statement disclosures. In November 2023, the FASB issued ASU 2023-07 "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures," which expands annual and interim disclosure requirements for reportable segments, primarily through enhanced disclosures about significant segment expenses. ASU 2023-07 is effective for the Company's annual periods beginning January 1, 2024, and for interim periods beginning January 1, 2025, with early adoption permitted. The Company is currently evaluating the potential effect that the updated standard will have on its financial statement disclosures. In December 2023, the FASB issued ASU 2023-09 "Income Taxes (Topics 740): Improvements to Income Tax Disclosures." The new standard requires expanded income tax disclosure of specific categories in the rate reconciliation and income taxes paid, disaggregated by jurisdiction. ASU 2023-09 is effective for the Company's annual periods beginning January 1, 2025, with early adoption and retrospective application permitted. The Company is currently evaluating the potential effect that the updated standard will have on its financial statement disclosures.

Unusual or Infrequently Occurri

Unusual or Infrequently Occurring Items (Tables)	12 Months Ended
	Dec. 31, 2023
Unusual or Infrequent Items, or Both [Abstract]
Restructuring and Related Costs	The table below summarizes special charges recorded during the years ended December 31, 2023, 2022, and 2021. Year Ended December 31, (in thousands) 2023 2022 2021 Sunseeker weather and related events $ 26,045 $ 52,095 $ — Sunseeker weather and related events, insurance recoveries (1) (32,491) (18,050) — Accelerated depreciation on airframes identified for early retirement 35,091 567 2,521 COVID-19 and related charges — — 11,477 Total special charges $ 28,645 $ 34,612 $ 13,998 (1) Includes $8.3 million of business interruption insurance proceeds for the year ended December 31, 2023. No business interruption insurance recoveries were received for the years ended December 31, 2022 or December 31, 2021.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Property, Plant and Equipment Estimated Useful Lives	The estimated useful lives of the principal asset classes are shown below. Aircraft, engines and related rotable parts 10 - 25 Years Buildings and leasehold improvements 10 - 39 Years Equipment 3 - 10 Years Computer hardware and software 3 - 15 Years Property and equipment consisted of the following: As of December 31, (in thousands) 2023 2022 Airline Flight equipment $ 3,346,216 $ 2,937,767 Computer hardware and software 274,927 209,808 Land and buildings/leasehold improvements 63,863 62,227 Other property and equipment 109,727 95,156 Sunseeker Resort Land and buildings/leasehold improvements 559,112 — Other property and equipment 53,743 — Construction in progress 4,389 320,572 Total property and equipment 4,411,977 3,625,530 Less accumulated depreciation and amortization (964,866) (814,837) Property and equipment, net $ 3,447,111 $ 2,810,693
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of net income per share on a basic and diluted basis for the periods indicated: Year ended December 31, (in thousands, except per share data) 2023 2022 2021 Basic: Net income $ 117,596 $ 2,493 $ 151,853 Less income allocated to participating securities (4,188) (32) (2,218) Net income attributable to common stock $ 113,408 $ 2,461 $ 149,635 Earnings per share, basic $ 6.32 $ 0.14 $ 8.69 Weighted-average shares outstanding 17,945 17,959 17,212 Diluted: Net income $ 117,596 $ 2,493 $ 151,853 Less income allocated to participating securities (4,175) (32) (2,215) Net income attributable to common stock $ 113,421 $ 2,461 $ 149,638 Earnings per share, diluted $ 6.29 $ 0.14 $ 8.68 Weighted-average shares outstanding 17,945 17,959 17,212 Dilutive effect of stock options and restricted stock 249 132 145 Adjusted weighted-average shares outstanding under treasury stock method 18,194 18,091 17,357 Participating securities excluded under two-class method (175) (57) (126) Adjusted weighted-average shares outstanding under two-class method 18,019 18,034 17,231

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	Passenger revenue is the most significant category in the Company's reported operating revenues, as outlined below: Year Ended December 31, (in thousands) 2023 2022 2021 Scheduled service $ 1,133,001 $ 1,062,753 $ 769,371 Ancillary air-related charges 1,137,226 1,025,549 788,064 Loyalty redemptions 54,170 49,460 21,001 Total passenger revenue $ 2,324,397 $ 2,137,762 $ 1,578,436
Contract with Customer, Asset and Liability	The following table presents the activity of the co-brand credit card and the loyalty program as of the dates indicated: Year Ended December 31, (in thousands) 2023 2022 Balance at January 1 $ 56,500 $ 40,449 Points awarded 68,483 65,511 Points redeemed (54,170) (49,460) Balance at December 31 $ 70,813 $ 56,500

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property Plant and Equipment	The estimated useful lives of the principal asset classes are shown below. Aircraft, engines and related rotable parts 10 - 25 Years Buildings and leasehold improvements 10 - 39 Years Equipment 3 - 10 Years Computer hardware and software 3 - 15 Years Property and equipment consisted of the following: As of December 31, (in thousands) 2023 2022 Airline Flight equipment $ 3,346,216 $ 2,937,767 Computer hardware and software 274,927 209,808 Land and buildings/leasehold improvements 63,863 62,227 Other property and equipment 109,727 95,156 Sunseeker Resort Land and buildings/leasehold improvements 559,112 — Other property and equipment 53,743 — Construction in progress 4,389 320,572 Total property and equipment 4,411,977 3,625,530 Less accumulated depreciation and amortization (964,866) (814,837) Property and equipment, net $ 3,447,111 $ 2,810,693

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Summary of Long-Term Debt	Long-term debt consisted of the following: As of December 31, (in thousands) 2023 2022 Fixed-rate debt and finance lease obligations due through 2032 $ 1,834,754 $ 1,720,998 Variable-rate debt due through 2029 424,900 375,980 Total long-term debt and finance lease obligations, net of related costs 2,259,654 2,096,978 Less current maturities, net of related costs 439,937 152,900 Long-term debt and finance lease obligations, net of current maturities and related costs $ 1,819,717 $ 1,944,078 Weighted average fixed-interest rate on debt 6.3 % 6.5 % Weighted average variable-interest rate on debt 7.9 % 6.1 % Interest Rate(s) Per Annum at As of December 31, (in thousands) Maturity Dates December 31, 2023 2023 2022 Senior secured notes 2027 7.25% $ 550,000 $ 700,000 Consolidated variable interest entities 2024 — 2029 2.92 % — 5.19% 130,650 79,453 Revolving credit facilities 2024 — 2027 7.97% 200,000 30,327 Debt secured by aircraft, engines, other equipment and real estate 2025 — 2031 1.87 % — 8.26% 596,271 466,335 Finance leases 2028 — 2032 4.44 % — 7.01% 455,248 494,328 Construction loan agreement 2028 5.75% 350,000 350,000 Total debt $ 2,282,169 $ 2,120,443 Related costs (22,515) (23,465) Total debt net of related costs $ 2,259,654 $ 2,096,978
Schedule of Maturities of Long-term Debt	Maturities of long-term debt as of December 31, 2023, for the next five years and thereafter, in the aggregate, are: (in thousands) As of December 31, 2023 2024 (1) 439,937 2025 180,611 2026 176,152 2027 709,354 2028 328,569 Thereafter 425,031 Total debt and finance lease obligations, net of related costs $ 2,259,654

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Schedule of Lease Cost	The components of lease costs recognized on the statements of income were as follows: Year Ended December 31, (in thousands) Classification on the Statements of Income 2023 2022 2021 Finance lease costs: Amortization of assets Depreciation and amortization $ 27,170 $ 17,579 $ 13,274 Interest on lease liabilities Interest expense 27,502 23,034 11,168 Operating lease cost Aircraft lease rentals; Station operations; Maintenance and repairs; Other operating expense 25,246 24,986 22,697 Variable lease cost Station operations; Maintenance and repairs; Other operating expense 1,563 1,469 2,565 Total lease cost $ 81,481 $ 67,068 $ 49,704
Schedule of Lease-related Asset and Liabilities	The table below presents the lease-related assets and liabilities recorded on the balance sheet. As of December 31, (in thousands) Classification on the Balance Sheet 2023 2022 Assets Operating lease assets Operating lease right-of-use assets, net $ 100,707 $ 111,679 Finance lease assets Property and equipment, net of accumulated depreciation 483,083 537,766 Total lease assets $ 583,790 $ 649,445 Liabilities Current Operating Current operating lease liabilities $ 20,873 $ 19,973 Finance Current maturities of long-term debt and finance lease obligations 25,352 39,080 Noncurrent Operating Noncurrent operating lease liabilities 82,410 94,972 Finance Long-term debt and finance lease obligations 429,896 455,248 Total lease liabilities $ 558,531 $ 609,273 Weighted-average remaining lease term Operating leases 7.4 years 7.0 years Finance leases 7.1 years 7.8 years Weighted-average discount rate Operating leases 5.5 % 5.4 % Finance leases 5.9 % 5.9 %
Schedule of Cash Flow, Supplemental Disclosures	The table below presents supplemental cash flow information related to leases during the years ended December 31, 2023 and 2022. Year Ended December 31, (in thousands) 2023 2022 2021 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows for operating leases $ 25,774 $ 25,775 $ 18,987 Operating cash flows for finance leases 27,672 22,366 10,697 Financing cash flows for finance leases 39,044 16,621 14,675
Schedule of Future Minimum Payments of Lease Liabilities	The table below indicates the future minimum payments of lease liabilities as of December 31, 2023. (in thousands) Operating Leases Finance Leases 2024 $ 25,912 $ 51,408 2025 23,850 51,408 2026 13,896 51,108 2027 11,688 51,108 2028 9,997 65,908 Thereafter 42,616 336,168 Total lease payments 127,959 607,108 Less imputed interest (24,676) (151,860) Total lease obligations 103,283 455,248 Less current obligations (20,873) (25,352) Long-term lease obligations $ 82,410 $ 429,896

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Schedule of Class of Treasury Stock	Share repurchases consisted of the following during the periods indicated: Year Ended December 31, 2023 2022 2021 Shares repurchased (1) 309,155 377,529 — Average price per share $ 78.61 $ 78.94 $ — Total (in thousands) $ 24,303 $ 29,802 $ — (1) Share amounts shown above include only open market repurchases and do not include shares withheld from employees for tax withholding obligations related to restricted stock vestings, which were 65,284, 1,423, and zero shares (not in thousands) for 2023, 2022, and 2021 respectively.
Schedule of Dividends Declared	Cash dividends declared by the Board and paid by the Company consisted of the following during the periods indicated: Year Ended December 31, 2023 2022 2021 Total quarterly cash dividends declared, per share $ 1.20 $ — $ — Total cash dividends paid (in thousands) 22,144 — —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value On a Recurring Basis	Financial instruments measured at fair value on a recurring basis: As of December 31, 2023 As of December 31, 2022 (in thousands) Total Level 1 Level 2 Total Level 1 Level 2 Cash equivalents Money market funds $ 33,613 $ 33,613 $ — $ 88,073 $ 88,073 $ — Commercial paper 19,575 — 19,575 50,791 — 50,791 Municipal debt securities 7,848 — 7,848 8,599 — 8,599 Federal agency debt securities 8,201 — 8,201 — — — US Treasury bonds 2,000 — 2,000 — — — Total cash equivalents 71,237 33,613 37,624 147,463 88,073 59,390 Short-term Commercial paper 237,870 — 237,870 421,279 — 421,279 Corporate debt securities 210,982 — 210,982 166,136 — 166,136 Federal agency debt securities 194,522 — 194,522 107,222 — 107,222 US Treasury Bonds 14,126 — 14,126 — — — Municipal debt securities 13,914 — 13,914 30,426 — 30,426 Total short-term 671,414 — 671,414 725,063 — 725,063 Long-term Corporate debt securities 43,869 — 43,869 35,688 — 35,688 Federal agency debt securities 12,135 — 12,135 20,050 — 20,050 Municipal debt securities — — — 7,580 — 7,580 Total long-term 56,004 — 56,004 63,318 — 63,318 Total financial instruments $ 798,655 $ 33,613 $ 765,042 $ 935,844 $ 88,073 $ 847,771
Debt Instrument, Fair Value Disclosure	Carrying value and estimated fair value of long-term debt, including current maturities and without reduction for related costs: As of December 31, 2023 As of December 31, 2022 (in thousands) Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Fair Value Level Non-publicly held debt $ 1,826,921 $ 1,815,351 $ 1,626,114 $ 1,561,939 3

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The provision (benefit) for income taxes is composed of the following: Year ended December 31, (in thousands) 2023 2022 2021 Current: Federal $ — $ 6 $ (494) State 3,306 73 552 Foreign 204 209 (6) Total current 3,510 288 52 Deferred: Federal 36,910 1,189 40,693 State 1,035 983 4,022 Total deferred 37,945 2,172 44,715 Total income tax provision $ 41,455 $ 2,460 $ 44,767
Schedule of Effective Income Tax Rate Reconciliation	The effective tax rate on income before income taxes differed from the federal statutory income tax rate as follows: Year ended December 31, (in thousands) 2023 2022 2021 Income tax expense at federal statutory rate $ 33,401 $ 1,040 $ 41,575 State income taxes, net of federal income tax benefit 3,503 1,189 4,257 Foreign income tax expense 204 210 (6) Executive compensation 3,692 57 2,359 Federal tax credits (2,034) (1,103) (385) Stock compensation 1,936 1,016 (2,058) Other 753 51 (975) Total income tax expense $ 41,455 $ 2,460 $ 44,767
Schedule of Deferred Tax Assets and Liabilities	The major components of the Company’s net deferred tax assets and liabilities are as follows: As of December 31, (in thousands) 2023 2022 Deferred tax assets: Employee benefits $ 8,410 $ 9,938 Net operating loss 22,237 30,370 Tax credits 4,128 4,290 Other (1) 30,576 18,644 Less: valuation allowance 1,214 1,214 Total deferred tax assets 64,137 62,028 Deferred tax liabilities: Prepaid expenses 4,516 4,223 Depreciation 434,620 399,622 Other 9,603 4,571 Total deferred tax liabilities 448,739 408,416 Net deferred tax liabilities $ 384,602 $ 346,388 (1) Other deferred tax assets consists of interest expense and research and development expenses.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Employee Benefit Plans [Abstract]
Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity	The following table provides information about the Company’s ESPP activity during 2023, 2022, and 2021: Year Ended Total number of shares purchased in year Average price paid per share Weighted-average fair value of discount under the ESPP (1) December 31, 2021 39,760 $ 174.68 $ 30.00 December 31, 2022 73,268 $ 97.85 $ 16.25 December 31, 2023 99,802 $ 85.27 $ 14.44 (1)
Schedule of Nonvested Restricted Stock Units Activity	A summary of the status of non-vested restricted stock grants during the y ears ended December 31, 2023, 2022 and 2021 is presented below: Shares Weighted Average Grant Date Fair Value Per Share Non-vested at December 31, 2020 265,527 $ 142.25 Granted 120,456 194.66 Vested (197,530) 136.71 Forfeited (6,900) 147.05 Non-vested at December 31, 2021 181,553 $ 183.63 Granted 374,540 89.31 Vested (74,170) 180.54 Forfeited (52,055) 123.01 Non-vested at December 31, 2022 429,868 $ 109.33 Granted 567,004 93.57 Vested (238,020) 119.00 Forfeited (151,459) 94.07 Non-vested at December 31, 2023 607,393 $ 94.64

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Contractual Obligation, Fiscal Year Maturity	The Company's contractual purchase commitments consist primarily of aircraft and engine acquisitions. The total future commitments are as follows: (in thousands) As of December 31, 2023 2024 $ 866,545 2025 673,612 2026 159,679 Total purchase commitments $ 1,699,836
Employees Under Collective Bargaining Agreements	The Company is party to collective bargaining agreements with the employee groups listed below. As of December 31, 2023, the percentage of full-time equivalent employees for each of these pay groups was as follows: As of December 31, 2023 Pilots 17.9 % Flight Attendants 23.4 Maintenance Technicians 11.2 Flight Dispatchers 0.9 Total 53.4 %

Segments (Tables)

Segments (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Selected information for the Company's segments and the reconciliation to the consolidated financial statement amounts are as follows: (in thousands) Airline Sunseeker Resort Consolidated Year Ended December 31, 2023 Operating revenue: Passenger $ 2,324,397 $ — $ 2,324,397 Third party products 112,579 — 112,579 Fixed fee contract 68,548 — 68,548 Other 1,444 2,889 4,333 Operating income (loss) 251,468 (30,487) 220,981 Interest income (46,615) — (46,615) Interest expense (1) 130,512 21,868 152,380 Capitalized interest (21,838) (23,294) (45,132) Depreciation and amortization 220,915 2,215 223,130 Capital expenditures 568,309 321,044 889,353 Year Ended December 31, 2022 Operating revenue: Passenger $ 2,137,762 $ — $ 2,137,762 Third party products 100,959 — 100,959 Fixed fee contract 60,937 — 60,937 Other 2,169 2 2,171 Operating income (loss) 136,968 (45,322) 91,646 Interest income (16,469) — (16,469) Interest expense (1) 92,785 16,046 108,831 Capitalized interest (4,308) (8,332) (12,640) Depreciation and amortization 197,433 109 197,542 Capital expenditures 475,254 288,408 763,662 Year Ended December 31, 2021 Operating revenue: Passenger $ 1,578,436 $ — $ 1,578,436 Third party products 86,487 — 86,487 Fixed fee contract 41,184 — 41,184 Other 1,803 — 1,803 Operating income (loss) 271,073 (7,998) 263,075 Interest income (1,814) — (1,814) Interest expense (1) 66,585 1,818 68,403 Depreciation and amortization 180,923 112 181,035 Capital expenditures 309,982 50,629 360,611 (1) Excludes losses on debt extinguishment. Total assets were as follows as of the dates indicated: (in thousands) As of December 31, 2023 As of December 31, 2022 Airline $ 4,213,288 $ 4,047,134 Sunseeker Resort 656,122 464,163 Consolidated $ 4,869,410 $ 4,511,297

Organization and Business of _2

Organization and Business of Company - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments	1

Special Charges - Narrative (De

Special Charges - Narrative (Details) $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 28, 2022 USD ($)	Sep. 30, 2023 Aircraft	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) Aircraft	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Unusual or Infrequent Item, or Both [Line Items]
Number Of Aircraft Retired | Aircraft		21		2
Total special charges				$ 28,645	$ 34,612	$ 13,998
Boeing 2021 Agreement
Unusual or Infrequent Item, or Both [Line Items]
Total special charges					35,100
Hurricane Ian
Unusual or Infrequent Item, or Both [Line Items]
Accelerated depreciation on airframes identified for early retirement	$ 52,100			35,091	567	2,521
Special Item - Impairment charges					18,100
Additional Non-Operating Special Charge				2,400
Sunseeker weather and related events				26,045	52,095	0
Sunseeker weather and related events, insurance recoveries(1)				32,491	18,050	$ 0
Insurance Recoveries				$ 1,000	$ 49,500
Hurricane Idalia
Unusual or Infrequent Item, or Both [Line Items]
Accelerated depreciation on airframes identified for early retirement			$ 23,600

Special Charges - Restructuring

Special Charges - Restructuring and Related Costs (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 28, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Unusual or Infrequent Item, or Both [Line Items]
Total special charges		$ 28,645	$ 34,612	$ 13,998
Proceeds from business interruption insurance		8,300
Hurricane Ian
Unusual or Infrequent Item, or Both [Line Items]
Sunseeker weather and related events		26,045	52,095	0
Sunseeker weather and related events, insurance recoveries(1)		(32,491)	(18,050)	0
Accelerated depreciation on airframes identified for early retirement	$ 52,100	35,091	567	2,521
COVID-19 and related charges		$ 0	$ 0	$ 11,477

Summary of Significant Accoun_4

Summary of Significant Accounting Policies Basis - Narrative (Details) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2021 point	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares
Property, Plant and Equipment [Line Items]
Inventory Valuation Reserves		$ 10.3	$ 8.1
Accounts Receivable, before Allowance for Credit Loss, Noncurrent		17	18.3
Capitalized Computer Software, Net		139.1	80.2
Capitalized Computer Software, Amortization		12.4	15.2	$ 10.6
Asset Impairment Charges		0
Advertising Expense		$ 41	$ 40.1	$ 31.3
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares		81,748	79,644	815
Allegiant Travel Company
Property, Plant and Equipment [Line Items]
Equity Method Investment, Ownership Percentage		50%
Allways Rewards Loyalty Program
Property, Plant and Equipment [Line Items]
Number Of Points Earned For Every Dollar Spent | point	1
Number Of Points Earned For Every Dollar Spent Over Five Hundred Dollars | point	2
A320 Series Engine
Property, Plant and Equipment [Line Items]
Deferred Costs for Heavy Maintenance		$ 68.5	$ 60.6
Amortization of Other Deferred Charges		$ 55.5	$ 43.8	$ 42.1
Minimum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		3 years
Maximum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		15 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Property, Plant and Equipment Estimated Useful Lives (Details)	Dec. 31, 2023
Minimum | Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Minimum | Equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Minimum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum | Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	39 years
Maximum | Equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Maximum | Computer hardware and software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Airbus A320 Aircraft Series | Minimum | Aircraft, engines and related rotable parts
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Airbus A320 Aircraft Series | Maximum | Aircraft, engines and related rotable parts
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	25 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest Cost [Abstract]
Net income	$ 117,596	$ 2,493	$ 151,853
Less income allocated to participating securities	(4,188)	(32)	(2,218)
Net income attributable to common stock	$ 113,408	$ 2,461	$ 149,635
Earnings Per Share, Basic	$ 6.32	$ 0.14	$ 8.69
Basic (in shares)	17,945	17,959	17,212
Less income allocated to participating securities	$ (4,175)	$ (32)	$ (2,215)
Net income attributable to common stock	$ 113,421	$ 2,461	$ 149,638
Diluted (in dollars per share)	$ 6.29	$ 0.14	$ 8.68
Dilutive effect of stock options and restricted stock (in shares)	249	132	145
Adjusted weighted-average shares outstanding under treasury stock method (in shares)	18,194	18,091	17,357
Participating securities excluded under two-class method (in shares)	(175)	(57)	(126)
Adjusted weighted-average shares outstanding under two-class method (in shares)		18,034	17,231

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Passenger	$ 2,324,397	$ 2,137,762	$ 1,578,436
Scheduled Service Revenue
Disaggregation of Revenue [Line Items]
Passenger	1,133,001	1,062,753	769,371
Air-related revenue
Disaggregation of Revenue [Line Items]
Passenger	1,137,226	1,025,549	788,064
Co-brand Revenue
Disaggregation of Revenue [Line Items]
Passenger	$ 54,170	$ 49,460	$ 21,001

Revenue Recognition - Narrative

Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Air traffic liability	$ 353,488	$ 379,459
Contract with Customer, Liability, Forward Bookings	303,600
Contract with Customer, Liability, Credit Voucher Bookings	$ 49,900
Revenue from Contract with Customer, Duration	12 months

Revenue Recognition - Contract

Revenue Recognition - Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Contract with Customer, Liability	$ 70,813	$ 56,500	$ 40,449
Points awarded	68,483	65,511
Points redeemed	$ 54,170	$ 49,460

Property and Equipment - Schedu

Property and Equipment - Schedule of Property Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Long-Lived Assets Held-for-Sale [Line Items]
Total property and equipment	$ 4,411,977	$ 3,625,530
Less accumulated depreciation and amortization	(964,866)	(814,837)
Property and equipment, net	3,447,111	2,810,693
Airline
Long-Lived Assets Held-for-Sale [Line Items]
Flight equipment	3,346,216	2,937,767
Computer hardware and software	274,927	209,808
Land and buildings/leasehold improvements	63,863	62,227
Other property and equipment	109,727	95,156
Sunseeker Resort
Long-Lived Assets Held-for-Sale [Line Items]
Land and buildings/leasehold improvements	559,112	0
Other property and equipment	53,743	0
Construction in progress	$ 4,389	$ 320,572

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Aircraft	Dec. 31, 2022 USD ($)
Property, Plant and Equipment [Abstract]
Number of aircraft committed to purchase | Aircraft	51
Capital Expenditures Incurred but Not yet Paid | $	$ 71.7	$ 54.6

Long-Term Debt - Summary of Lon

Long-Term Debt - Summary of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Aug. 31, 2022
Debt Instrument [Line Items]
Carrying Value	$ 2,259,654	$ 2,096,978
Long-term Debt, Current Maturities	439,937	152,900
Long-term Debt, Excluding Current Maturities	$ 1,819,717	$ 1,944,078
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Debt and Lease Obligation	Debt and Lease Obligation
Total lease obligations	$ 455,248	$ 494,328
Debt and Lease Obligation	2,282,169	2,120,443
Debt Issuance Costs, Net	$ (22,515)	(23,465)
Minimum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.44%
Maximum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.01%
Fixed Rate
Debt Instrument [Line Items]
Notes Payable	$ 1,834,754	$ 1,720,998
Long-term Debt, Weighted Average Interest Rate, at Point in Time	6.30%	6.50%
Variable Rate
Debt Instrument [Line Items]
Notes Payable	$ 424,900	$ 375,980
Long-term Debt, Weighted Average Interest Rate, at Point in Time	7.90%	6.10%
Revolving Credit Facilities Due 2027 | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 200,000	$ 30,327
Debt Instrument, Interest Rate, Stated Percentage	7.97%
Senior Secured Notes Due 2027 | Senior Notes
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 550,000	700,000
Debt Instrument, Interest Rate, Stated Percentage			7.25%
Senior Secured Notes Due 2027 | Senior Notes | Maximum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.25%
Consolidated Variable Interest Entities Due 2029
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 130,650	79,453
Consolidated Variable Interest Entities Due 2029 | Minimum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.92%
Consolidated Variable Interest Entities Due 2029 | Maximum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.19%
Secured Debt By Aircraft, Engines, Other Equipment And Real Estate | Secured Debt
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 596,271	466,335
Secured Debt By Aircraft, Engines, Other Equipment And Real Estate | Secured Debt | Minimum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.87%
Secured Debt By Aircraft, Engines, Other Equipment And Real Estate | Secured Debt | Maximum
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.26%
Construction Loan Agreement Due 2032
Debt Instrument [Line Items]
Long-term Debt, Excluding Current Maturities	$ 350,000	$ 350,000
Debt Instrument, Interest Rate, Stated Percentage	5.75%

Long-Term Debt - Schedule of Ma

Long-Term Debt - Schedule of Maturities of Long-term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
2024(1)	$ 439,937
2025	180,611
2026	176,152
2027	709,354
2028	328,569
Thereafter	425,031
Total debt and finance lease obligations, net of related costs	$ 2,259,654	$ 2,096,978

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Detail) $ in Millions	1 Months Ended				12 Months Ended
	Nov. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Aug. 31, 2022 USD ($)	Oct. 31, 2021 USD ($)	Dec. 31, 2023 USD ($) Aircraft	Sep. 30, 2023 USD ($)	May 31, 2023 USD ($)	Feb. 28, 2023 USD ($)	Mar. 31, 2021 USD ($)
Debt Instrument [Line Items]
Assets At Carrying Value					$ 51.6
Liabilities At Carrying Value					$ 63
Line of credit facility, maximum borrowing capacity	$ 158		$ 75				$ 92.7
Number Of Aircraft, Finance Lease Obligation | Aircraft					23
Collateralized Agreements					$ 63
Revolving Credit Facility
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	113.9
Repayments of Lines of Credit					207.8
Revolving Credit Facility | MUFG Bank, Ltd
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			100
Revolving Credit Facility | Landesbank Hessen-Thüringen Girozentrale
Debt Instrument [Line Items]
Line of credit facility, expiration period		24 months
Line of Credit Facility, Commitment Fee Amount		$ 200
Extinguishment of Debt, Amount					$ 200
Revolving Credit Facility | Credit Agricole Corporate and Investment Bank
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity								$ 100	$ 50
Revolving Credit Facility | BNP Paribas And Jackson Square Aviation
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity									$ 412.1
Line of Credit, Current						$ 196.4
Senior Secured Revolving Loan Facility | Barclays Bank PLC
Debt Instrument [Line Items]
Long-Term Line of Credit			$ 75
Line of credit facility, expiration period			57 months
Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Convertible, Liquidation Preference, Value			$ 300
Debt Instrument, Liquidation Requirement, Interest Percentage			0.020
Consolidated Variable Interest Entity
Debt Instrument [Line Items]
Number of aircrafts included as collateral | Aircraft					6
Delayed-Draw Construction Loan | Sunseeker Resort
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 350
Debt Instrument, Interest Rate, Stated Percentage				5.75%
Debt Instrument, Periodic Payment, Principal				$ 26
Senior Secured Notes Due 2027 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 550
Debt Instrument, Interest Rate, Stated Percentage			7.25%
Senior Secured Notes due 2024 [Member] | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150
Debt Instrument, Interest Rate, Stated Percentage	8.50%
Long-Term Debt, Percentage Bearing Fixed Interest, Percentage Rate			7.25%

Leases - Narrative (Details)

Leases - Narrative (Details)	Dec. 31, 2023 Aircraft
Leases [Abstract]
Finance Leased Assets, Number Of Units	23
Operating Leased Assets, Number Of Units	17

Leases - Schedule of Lease Cost

Leases - Schedule of Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Amortization of assets	$ 27,170	$ 17,579	$ 13,274
Interest on lease liabilities	27,502	23,034	11,168
Operating lease cost	25,246	24,986	22,697
Variable lease cost	1,563	1,469	2,565
Total lease cost	$ 81,481	$ 67,068	$ 49,704

Leases - Schedule of Lease-rela

Leases - Schedule of Lease-related Asset and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
operating right of use asset, net	$ 100,707	$ 111,679
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property and equipment (including $129,646 and $80,591 from VIEs, Note 6), net of accumulated depreciation of $964,866 and $814,837	Property and equipment (including $129,646 and $80,591 from VIEs, Note 6), net of accumulated depreciation of $964,866 and $814,837
Finance Lease, Right-of-Use Asset	$ 483,083	$ 537,766
Total Right-of-Use Asset	583,790	649,445
Current operating lease liabilities	20,873	19,973
Finance Lease, Liability, Current	25,352	39,080
Noncurrent operating lease liabilities	82,410	94,972
Long-term lease obligations	429,896	455,248
Total Lease Liability	$ 558,531	$ 609,273
Operating Lease, Weighted Average Remaining Lease Term	7 years 4 months 24 days	7 years
Finance Lease, Weighted Average Remaining Lease Term	7 years 1 month 6 days	7 years 9 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	5.50%	5.40%
Finance Lease, Weighted Average Discount Rate, Percent	5.90%	5.90%

Leases - Schedule of Cash Flow,

Leases - Schedule of Cash Flow, Supplemental Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating cash flows for operating leases	$ 25,774	$ 25,775	$ 18,987
Operating cash flows for finance leases	27,672	22,366	10,697
Financing cash flows for finance leases	$ 39,044	$ 16,621	$ 14,675

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Payments of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases, Operating [Abstract]
2024	$ 25,912
2025	23,850
2026	13,896
2027	11,688
2028	9,997
Thereafter	42,616
Total lease payments	127,959
Less imputed interest	(24,676)
Total lease obligations	103,283
Accrued liabilities	(20,873)	$ (19,973)
Noncurrent operating lease liabilities	82,410	94,972
Finance Lease, Liability [Abstract]
2024	51,408
2025	51,408
2026	51,108
2027	51,108
2028	65,908
Thereafter	336,168
Total lease payments	607,108
Less imputed interest	(151,860)
Total lease obligations	455,248	494,328
Less current obligations	(25,352)	(39,080)
Long-term lease obligations	$ 429,896	$ 455,248
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Debt and Lease Obligation	Debt and Lease Obligation

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Class of Treasury Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity [Abstract]
Shares repurchased (in shares)	309,155	377,529	0
Average price per share (in dollars per share)	$ 78.61	$ 78.94	$ 0
Total (in thousands)	$ 24,303	$ 29,802	$ 0
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation	65,284	1,423	0

Shareholders_ Equity - Schedule

Shareholders’ Equity - Schedule of Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity [Abstract]
Total quarterly cash dividends declared (in dollars per share)	$ 1.20	$ 0	$ 0
Total cash dividends paid (in thousands)	$ 22,144	$ 0	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets Measured at Fair Value On a Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale	$ 798,655	$ 935,844
Cash equivalents
Cash Equivalents	71,237	147,463
Short-term
Debt Securities, Available-for-Sale	671,414	725,063
Long-term
Debt Securities, Available-for-Sale	56,004	63,318
Level 1
Debt Securities, Available-for-Sale	33,613	88,073
Level 1 | Cash equivalents
Cash Equivalents	33,613	88,073
Level 1 | Short-term
Debt Securities, Available-for-Sale	0	0
Level 1 | Long-term
Debt Securities, Available-for-Sale	0	0
Level 2
Debt Securities, Available-for-Sale	765,042	847,771
Level 2 | Cash equivalents
Cash Equivalents	37,624	59,390
Level 2 | Short-term
Debt Securities, Available-for-Sale	671,414	725,063
Level 2 | Long-term
Debt Securities, Available-for-Sale	56,004	63,318
Money market funds | Cash equivalents
Cash Equivalents	33,613	88,073
Money market funds | Level 1 | Cash equivalents
Cash Equivalents	33,613	88,073
Money market funds | Level 2 | Cash equivalents
Cash Equivalents	0	0
Commercial paper | Cash equivalents
Cash Equivalents	19,575	50,791
Commercial paper | Short-term
Debt Securities, Available-for-Sale	237,870	421,279
Commercial paper | Level 1 | Cash equivalents
Cash Equivalents	0	0
Commercial paper | Level 1 | Short-term
Debt Securities, Available-for-Sale	0	0
Commercial paper | Level 2 | Cash equivalents
Cash Equivalents	19,575	50,791
Commercial paper | Level 2 | Short-term
Debt Securities, Available-for-Sale	237,870	421,279
Federal agency debt securities | Cash equivalents
Cash Equivalents	8,201	0
Federal agency debt securities | Short-term
Debt Securities, Available-for-Sale	194,522	107,222
Federal agency debt securities | Long-term
Debt Securities, Available-for-Sale	12,135	20,050
Federal agency debt securities | Level 1 | Cash equivalents
Cash Equivalents	0	0
Federal agency debt securities | Level 1 | Short-term
Debt Securities, Available-for-Sale	0	0
Federal agency debt securities | Level 1 | Long-term
Debt Securities, Available-for-Sale	0	0
Federal agency debt securities | Level 2 | Cash equivalents
Cash Equivalents	8,201	0
Federal agency debt securities | Level 2 | Short-term
Debt Securities, Available-for-Sale	194,522	107,222
Federal agency debt securities | Level 2 | Long-term
Debt Securities, Available-for-Sale	12,135	20,050
US Treasury bonds | Cash equivalents
Cash Equivalents	2,000	0
US Treasury bonds | Short-term
Debt Securities, Available-for-Sale	14,126	0
US Treasury bonds | Level 1 | Cash equivalents
Cash Equivalents	0	0
US Treasury bonds | Level 1 | Short-term
Debt Securities, Available-for-Sale	0	0
US Treasury bonds | Level 2 | Cash equivalents
Cash Equivalents	2,000	0
US Treasury bonds | Level 2 | Short-term
Debt Securities, Available-for-Sale	14,126	0
Municipal debt securities | Cash equivalents
Cash Equivalents	7,848	8,599
Municipal debt securities | Short-term
Debt Securities, Available-for-Sale	13,914	30,426
Municipal debt securities | Long-term
Debt Securities, Available-for-Sale	0	7,580
Municipal debt securities | Level 1 | Cash equivalents
Cash Equivalents	0	0
Municipal debt securities | Level 1 | Short-term
Debt Securities, Available-for-Sale	0	0
Municipal debt securities | Level 1 | Long-term
Debt Securities, Available-for-Sale	0	0
Municipal debt securities | Level 2 | Cash equivalents
Cash Equivalents	7,848	8,599
Municipal debt securities | Level 2 | Short-term
Debt Securities, Available-for-Sale	13,914	30,426
Municipal debt securities | Level 2 | Long-term
Debt Securities, Available-for-Sale	0	7,580
Corporate debt securities | Short-term
Debt Securities, Available-for-Sale	210,982	166,136
Corporate debt securities | Long-term
Debt Securities, Available-for-Sale	43,869	35,688
Corporate debt securities | Level 1 | Short-term
Debt Securities, Available-for-Sale	0	0
Corporate debt securities | Level 1 | Long-term
Debt Securities, Available-for-Sale	0	0
Corporate debt securities | Level 2 | Short-term
Debt Securities, Available-for-Sale	210,982	166,136
Corporate debt securities | Level 2 | Long-term
Debt Securities, Available-for-Sale	$ 43,869	$ 35,688

Fair Value Measurements - Debt

Fair Value Measurements - Debt Instrument, Fair Value Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 2,259,654	$ 2,096,978
Non-publicly held debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	1,826,921	1,626,114
Fair Value, Inputs, Level 3 | Non-publicly held debt | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	$ 1,815,351	$ 1,561,939

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income before Income Tax, Domestic and Foreign (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Domestic	$ 159,051	$ 4,953	$ 196,620
Foreign	0	0	0
INCOME BEFORE INCOME TAXES	$ 159,051	$ 4,953	$ 196,620

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal	$ 0	$ 6	$ (494)
State	3,306	73	552
Foreign	204	209	(6)
Total current	3,510	288	52
Federal	36,910	1,189	40,693
State	1,035	983	4,022
Total deferred	37,945	2,172	44,715
Total income tax provision	$ 41,455	$ 2,460	$ 44,767

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income tax expense at federal statutory rate	$ 33,401	$ 1,040	$ 41,575
State income taxes, net of federal income tax benefit	3,503	1,189	4,257
Foreign income tax expense	204	210	(6)
Executive compensation	3,692	57	2,359
Federal tax credits	(2,034)	(1,103)	(385)
Stock compensation	1,936	1,016	(2,058)
Other	753	51	(975)
Total income tax provision	$ 41,455	$ 2,460	$ 44,767

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Employee benefits	$ 8,410	$ 9,938
Net operating loss	22,237	30,370
Tax credits	4,128	4,290
Other(1)	30,576	18,644
Less: valuation allowance	1,214	1,214
Total deferred tax assets	64,137	62,028
Prepaid expenses	4,516	4,223
Depreciation	434,620	399,622
Other	9,603	4,571
Total deferred tax liabilities	448,739	408,416
Net deferred tax liabilities	$ 384,602	$ 346,388

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) $ in Millions	Dec. 31, 2023 USD ($)
Domestic Tax Authority
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 14
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Operating Loss Carryforwards	$ 8.2

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2015
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Defined contribution plan, maximum annual contribution per employee, percent	90%			25%
Defined contribution plan, cost	$ 25,500,000	$ 24,000,000	$ 21,400,000
Share-based compensation arrangement by share-based payment award, number of shares authorized	2,000,000
Shares held in employee stock option plan, allocated				1,000,000
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount				$ 25,000
Share-based compensation expense	$ 29,749,000	15,198,000	16,127,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	39,700,000
Cash-settled SARs	100,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	28,300,000	13,400,000	27,000,000
Restricted Stock, Stock Options, Cash-Settled SARs And Employee Stock Purchase Program
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Share-based compensation expense	$ 31,500,000	$ 16,300,000	$ 17,200,000
Restricted Stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	2 years 8 months 8 days
Employee
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Defined contribution plan, employer matching contribution, percent of employees' gross pay	5%

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Postemployment Benefits [Abstract]
Total number of shares purchased in year	99,802	73,268	39,760
Average price paid per share (in dollars per share)	$ 85.27	$ 97.85	$ 174.68
Weighted-average fair value of discount under the ESPP	$ 14.44	$ 16.25	$ 30

Employee Benefit Plans - Sche_2

Employee Benefit Plans - Schedule of Nonvested Restricted Stock Units Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested, beginning balance (in shares)	429,868	181,553	265,527
Granted (in shares)	567,004	374,540	120,456
Vested (in shares)	(238,020)	(74,170)	(197,530)
Forfeited (in shares)	(151,459)	(52,055)	(6,900)
Non-vested, ending balance (in shares)	607,393	429,868	181,553
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested, beginning balance, weighted average grant date fair value (in dollars per share)	$ 109.33	$ 183.63	$ 142.25
Granted, weighted average grant date fair value (in dollars per share)	93.57	89.31	194.66
Vested, weighted average grant date fair value (in dollars per share)	119	180.54	136.71
Forfeited, weighted average grant date fair value (in dollars per share)	94.07	123.01	147.05
Non-vested, ending balance, weighted average grant date fair value (in dollars per share)	$ 94.64	$ 109.33	$ 183.63

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Contractual Obligation, Fiscal Year Maturity (Detail) $ in Thousands	Dec. 31, 2023 USD ($) Aircraft
Commitments and Contingencies Disclosure [Abstract]
2024	$ 866,545
2025	673,612
2026	159,679
Total purchase commitments	$ 1,699,836
Number of aircraft committed to purchase | Aircraft	51

Commitment and Contingencies -

Commitment and Contingencies - Employees Under Collective Bargaining Agreements (Details)	12 Months Ended
	Dec. 31, 2023
Pilots | Unionized Employees Concentration Risk
Other Commitments [Line Items]
Concentration risk, percentage	17.90%
Flight Attendants | Unionized Employees Concentration Risk
Other Commitments [Line Items]
Concentration risk, percentage	23.40%
Maintenance Technicians | Unionized Employees Concentration Risk
Other Commitments [Line Items]
Concentration risk, percentage	11.20%
Flight Dispatchers | Unionized Employees Concentration Risk
Other Commitments [Line Items]
Concentration risk, percentage	0.90%
Total
Other Commitments [Line Items]
Concentration risk, percentage	41.30%
Total | Unionized Employees Concentration Risk
Other Commitments [Line Items]
Concentration risk, percentage	53.40%

Commitments and Contingencies_2

Commitments and Contingencies - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 employee Aircraft
Other Commitments [Line Items]
Number of aircraft committed to purchase | Aircraft	51
Number of full-time equivalent employee | employee	6,700
Total
Other Commitments [Line Items]
Concentration risk, percentage	41.30%

Segments - Narrative (Details)

Segments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) segment
Segment Reporting Information [Line Items]
Number of operating segments | segment	2
Preopening Expense | $	$ 26.5

Segments - Schedule of Segment

Segments - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Passenger	$ 2,324,397	$ 2,137,762	$ 1,578,436
Third party products	112,579	100,959	86,487
Fixed fee contract	68,548	60,937	41,184
Other	4,333	2,171	1,803
Operating income (loss)	220,981	91,646	263,075
Interest income	(46,615)	(16,469)	(1,814)
Interest expense	152,380	108,831	68,403
Capitalized interest	(45,132)	(12,640)
Depreciation and amortization	223,130	197,542	181,035
Capital expenditures	889,353	763,662	360,611
Assets	4,869,410	4,511,297
Allegiant Air
Segment Reporting Information [Line Items]
Passenger	2,324,397	2,137,762	1,578,436
Third party products	112,579	100,959	86,487
Fixed fee contract	68,548	60,937	41,184
Other	1,444	2,169	1,803
Operating income (loss)	251,468	136,968	271,073
Interest income	(46,615)	(16,469)	(1,814)
Interest expense	130,512	92,785	66,585
Capitalized interest	(21,838)	(4,308)
Depreciation and amortization	220,915	197,433	180,923
Capital expenditures	568,309	475,254	309,982
Assets	4,213,288	4,047,134
Sunseeker Resort
Segment Reporting Information [Line Items]
Passenger	0	0	0
Third party products	0	0	0
Fixed fee contract	0	0	0
Other	2,889	2	0
Operating income (loss)	(30,487)	(45,322)	(7,998)
Interest income	0	0	0
Interest expense	21,868	16,046	1,818
Capitalized interest	(23,294)	(8,332)
Depreciation and amortization	2,215	109	112
Capital expenditures	321,044	288,408	$ 50,629
Assets	$ 656,122	$ 464,163

Uncategorized Items - algt-2023

Label	Element	Value
Parent [Member]
Dividends, Cash	us-gaap_DividendsCash	$ (22,144,000)
Retained Earnings [Member]
Dividends, Cash	us-gaap_DividendsCash	$ (22,144,000)