Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2025
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of Harbor Diversified, Inc. (“Harbor”) and its consolidated subsidiaries, which are collectively referred to in these condensed notes as the “Company”. The condensed consolidated financial statements have been prepared, without audit, in conformity with accounting principles generally accepted in the United States of America (“GAAP”), and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to SEC rules and regulations, although the Company believes that the following disclosures are adequate to make the information presented not misleading. The condensed consolidated financial statements reflect all adjustments that, in the opinion of management, are necessary to present fairly, in all material respects, the financial condition and results of operations for the interim periods presented. All adjustments are of a normal recurring nature, unless otherwise disclosed. All of the dollar and share amounts set forth in these condensed notes to the condensed consolidated financial statements are presented in thousands except share amounts and per share values. Harbor is a non-operating holding company that is the parent of a consolidated group of wholly-owned subsidiaries, including AWAC Aviation, Inc. (“AWAC”), which was the sole member of Air Wisconsin Airlines LLC (“Air Wisconsin”), which historically operated as a regional air carrier. Harbor is also the direct parent of three other subsidiaries: (1) Lotus Aviation Leasing, LLC (“Lotus”), which leased flight equipment to Air Wisconsin, (2) Air Wisconsin Funding LLC (“AWF”), which provided flight equipment financing to Air Wisconsin, and (3) Harbor Therapeutics, Inc. (“Therapeutics”), which is a non-operating entity with no material assets. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in Harbor’s Annual Report on Form 10-K for the year ended December 31, 2024, which was filed with the SEC on April 8, 2025 (the “2024 Annual Report”). As a result of numerous factors, including those discussed throughout this Quarterly Report, the results of operations for the three and nine months ended September 30, 2025 are not necessarily indicative of the results that may be expected for any other reporting period.
Aviation Disposition	Aviation Disposition On January 9, 2026, Harbor completed the last in a series of transactions pursuant to which it disposed of all of its aviation assets, including its membership interests in Air Wisconsin (the completion of all such transactions, collectively, the “Aviation Disposition”) for which it received approximately $125,900, in the aggregate, subject to certain customary purchase price adjustments and the impact of required tax obligations. After giving effect to the Aviation Disposition, neither Harbor nor any of its remaining subsidiaries has any material operating assets or infrastructure to support an airline, provided that the Company did retain certain non-operating assets, which primarily relate to lease payments for a single aircraft, insurance claims, and state and federal tax refunds. Harbor currently does not have any material operating assets, is not engaged in any operating business, and does not have any source of revenue from operations.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts and transactions of Harbor and its wholly-owned subsidiaries. All inter-company accounts and transactions are eliminated in consolidation.
Description of Operations	Description of Operations During the periods presented in this Quarterly Report, the Company had principal lines of business focused on (1) providing regional and other air services through Air Wisconsin (airline business), (2) acquiring flight equipment for the purpose of leasing the equipment to Air Wisconsin, and (3) providing flight equipment financing to Air Wisconsin. However, on April 3, 2025, the American capacity purchase agreement was terminated. As part of the wind-down schedule delivered by American Airlines, Inc. (“American”) in connection with the termination of the capacity purchase agreement entered into between Air Wisconsin and American in August 2022 (“American capacity purchase agreement”), 15 aircraft were removed from service in March 2025, with the remaining aircraft removed from service for American on April 3, 2025. As of September 30, 2025, Air Wisconsin had no aircraft in service under the American capacity purchase agreement. Following the termination of the American capacity purchase agreement, Air Wisconsin no longer operated as a regional air carrier. During the three months ended September 30, 2025, in addition to charter operations discussed below that commenced in the fourth quarter of 2024, the Company explored alternative business strategies, including the sale and lease of assets, and the Company sold two aircraft, each consisting of an airframe and two engines, along with two additional engines. However, these efforts did not lead to sustainable operations or positive financial results and ultimately resulted in the Aviation Disposition. Following completion of the sale of the two aircraft, the Company agreed to perform certain maintenance services with respect to the aircraft. The Company recorded service revenues of $377 for both the three and nine months ended September 30, 2025 which is recorded in Contract services and other in the condensed consolidated statements of operations. This service revenue accounted for 41.7% and 0.6% of Total operating revenues for the three and nine months ended September 30, 2025, respectively. In the fourth quarter of 2024, Air Wisconsin began offering on-demand charter service within the contiguous United States. This service was seasonal in nature with a significant portion of charter flights provided to collegiate athletic teams, whose seasons typically end in late spring or early summer and do not begin again until fall. For additional information, please refer to Note 2, Capacity Purchase Agreement with American, and Note 13, Subsequent Events.
Segment Reporting	Segment Reporting Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker (“CODM”), who for the three and nine months ended September 30, 2025, was the President and Chief Executive Officer of Air Wisconsin, in deciding how to allocate resources and assess operating performance. Under Accounting Standards Codification Topic 280, Segment Reporting, for the three and nine months ended September 30, 2025, the Company had one reportable segment that was managed on a consolidated basis, which provided scheduled flight services for American under the American capacity purchase agreement and on-demand charter service within the contiguous United States and Canada. Our CODM evaluated the Company's financial information and resources on a consolidated net income basis. Significant expenses that are regularly provided to the CODM for the Company's one reportable segment are presented on the consolidated statements of operations and are included within the reported measure of consolidated Net income. Additionally, the measure of segment assets is reported on the consolidated balance sheets as Total assets.
Contract Revenues and Contract Assets and Liabilities	Contract Revenues For the three and nine months ended September 30, 2025, approximately —% and 84.9%, respectively, of the Company’s Total operating revenues were derived from operations associated with the American capacity purchase agreement. For the three and nine months ended September 30, 2024, approximately 100.0% of the Company's Total operating revenues were derived from operations associated with the American capacity purchase agreement. In performing an analysis of the American capacity purchase agreement within the framework of Accounting Standards Update (“ASU”) No. 2016-02, Leases (“ASC 842”) and Accounting Standards Codification Topic 606, Revenue from Contracts with Customers (“ASC 606”), the Company determined that a portion of the payments it received under the American capacity purchase agreement that was designated to reimburse Air Wisconsin for use of a certain number of aircraft, which is referred to as “right of use,” was considered lease revenue. All other revenue received by Air Wisconsin under the American capacity purchase agreement was considered non-lease revenue. After consideration of the lease and non-lease components, within the context of ASC 842, the Company determined the non-lease component to be the predominant component of the American capacity purchase agreement and elected a practical expedient to not separate the lease and non-lease components. Therefore, all compensation received by Air Wisconsin pursuant to the American capacity purchase agreement was accounted for under ASC 606. Because Air Wisconsin's flights were distinct services that had the same pattern of transfer to the customer, which were satisfied over time with the measure of progress for each flight deemed to be substantially the same, the flight services promised pursuant to the American capacity purchase agreement represented a series of services that were accounted for as a single performance obligation. Therefore, contract revenues were recognized when service was provided and the performance obligation was met on a per completed flight basis. The performance obligation of each completed flight was measured using departures. Under the American capacity purchase agreement Air Wisconsin was entitled to receive certain payments based on the number of aircraft covered under the agreement, block hours, departures and certain performance metrics. During the three and nine months ended September 30, 2025, Air Wisconsin received $0 and $17,946, respectively, related to flying based on block hours and departures, compared to $23,656 and $67,154, respectively, for the three and nine months ended September 30, 2024. The American capacity purchase agreement also provided for the reimbursement to Air Wisconsin of certain direct operating expenses, such as certain insurance premiums and property taxes. Air Wisconsin was also eligible to receive bonus compensation, and was required to pay rebates, upon the achievement of, or failure to achieve, certain pre-established performance criteria. In November 2024, Air Wisconsin and American entered into Amendment No. 4 to the American capacity purchase agreement (“Amendment No. 4”) which, among other things (i) resolved certain disputes with respect to the interpretation of American's payment obligations under the American capacity purchase agreement, (ii) accelerated the right of each of Air Wisconsin and American to terminate the American capacity purchase agreement for convenience, (iii) modified the way in which compensation rates and bonus and rebate reconciliations were made, (iv) modified the total number of aircraft and total number of hours for which Air Wisconsin received payment, and (v) provided for certain incentive payments made by American to Air Wisconsin. Prior to the termination of the American capacity purchase agreement, American made provisional cash payments to Air Wisconsin during each month of service based on projected flight schedules. The provisional cash payments were subsequently reconciled with American based on actual completed flight activity. As of September 30, 2025 and December 31, 2024, American owed Air Wisconsin $0 and $3,395, respectively, which is recorded in Receivables, net, in the condensed consolidated balance sheets. As of the date of this filing, all payments under the American capacity purchase agreement have been reconciled. Air Wisconsin was eligible under the American capacity purchase agreement, as amended by Amendment No. 4, to receive bonus payments, and was required to pay rebates, upon the achievement of, or failure to achieve, certain performance criteria primarily based on flight completion, on-time performance, and customer satisfaction ratings. At the end of each month or quarter, Air Wisconsin calculated the bonus amounts achieved, or rebates payable, during that period and recognized revenue accordingly, subject to the variable constraint guidance under ASC 606. For the three and nine months ended September 30, 2025, Air Wisconsin recorded $0 and $4,500, respectively, in incentive amounts under the American capacity purchase agreement. For the three and nine months ended September 30, 2024, Air Wisconsin recorded $207 and $862, respectively, in net rebate amounts payable under the American capacity purchase agreement. Under the American capacity purchase agreement, as amended by Amendment No. 4, Air Wisconsin was entitled to receive from American a fixed daily amount for each aircraft covered under the agreement. Because the fixed daily amounts for each aircraft covered under the agreement were specifically related to the performance obligation completed during the period, they were recognized in contract revenues in the period in which the applicable flights were completed. During the three and nine months ended September 30, 2025, Air Wisconsin recorded $0 and $16,029, respectively, of fixed daily revenues under the American capacity purchase agreement which are included as part of Contract revenues in the condensed consolidated statements of operations, compared to $21,792 and $63,908, respectively, of fixed daily revenues recorded under the agreement for the three and nine months ended September 30, 2024. Under the American capacity purchase agreement, Air Wisconsin was also entitled to be reimbursed for certain startup costs, such as livery changes to the aircraft, to prepare the aircraft for American flight services that it recognized as non-refundable upfront fee revenue. As of September 30, 2025, Air Wisconsin had incurred $3,998 in reimbursable costs. In accordance with GAAP, the Company recognized revenue related to the total estimated non-refundable upfront fee revenue on a proportional basis taking into account the number of flights actually completed in the period relative to the number of flights expected to be completed in subsequent periods during the remaining term of the agreement. Accordingly, during the three and nine months ended September 30, 2025, Air Wisconsin recognized $0 and $753, respectively, of non-refundable upfront fee revenues that were previously deferred compared to $1,558 and $1,900 for the three and nine months ended September 30, 2024. As of September 30, 2025 and December 31, 2024, Air Wisconsin deferred $0, and $753, respectively, in non-refundable upfront fee revenues under the American capacity purchase agreement. Air Wisconsin’s deferred revenues related to the non-refundable upfront fee revenues under the American capacity purchase agreement were adjusted over the remaining contract term, based on the actual expenses incurred that were reimbursed and recognized based on the number of flights actually completed in the period relative to the number of flights expected to be completed in subsequent periods during the remaining term of the agreement. As of September 30, 2025 there were no longer any deferred upfront fee revenues due to the termination of the American capacity purchase agreement in April 2025. As of December 31, 2024, deferred non-refundable upfront fee revenues in the amount of $753 were netted as part of Contract liabilities, net in the condensed consolidated balance sheets. Under the American capacity purchase agreement, Air Wisconsin also received a monthly support fee and was reimbursed for heavy maintenance expenses based on the fixed covered per aircraft per day rate over the term of the agreement. In addition, amendments to the American capacity purchase agreement entered into in February 2023 and November 2023 (“Amendment No. 1” and “Amendment No. 3”, respectively) provided for a one-time payment, as well as revised compensation rates, to assist Air Wisconsin with pilot compensation and retention. Amendment No. 4 provided payment for a fixed number of aircraft through the term of the American capacity purchase agreement. In accordance with GAAP, the Company recognized revenue related to the monthly support fee, heavy maintenance revenue, and one-time pilot compensation assistance payment on a proportional basis taking into account the number of flights actually completed in the period relative to the number of flights expected to be completed in subsequent periods during the remaining term of the agreement. Accordingly, during the three and nine months ended September 30, 2025, Air Wisconsin recognized $0 and $2,998 of revenue related to these revenue streams compared to $2,176 and $5,982 for the three and nine months ended September 30, 2024. As of September 30, 2025 there were no longer any deferred revenues related to monthly support fees, the one-time pilot compensation assistance payment, or reimbursed heavy maintenance expenses. As of December 31, 2024 revenues related to the anticipated heavy maintenance reimbursements, one-time pilot compensation assistance payment and monthly support fee in the amounts of $2,689 were netted as part of Contract liabilities, net in the condensed consolidated balance sheets. Air Wisconsin’s Contract liabilities, net related to the heavy maintenance revenue, one-time pilot compensation assistance payment, and monthly support fee were adjusted over the remaining contract term, based on the actual reimbursement of the monthly support fee and heavy maintenance revenue and on the number of flights actually completed in each reporting period relative to the number of flights that were completed in subsequent periods during the remaining term of the agreement. Under the American capacity purchase agreement, Air Wisconsin was eligible to receive a block hour minimum and fixed daily amount for aircraft when flying scheduled by American did not meet minimum thresholds based on Air Wisconsin's crew availability (“block hour and crew availability minimums”). Since the start of flying under the American capacity purchase agreement in March 2023, in all periods prior to March 31, 2024, American had met such minimum thresholds and thus no minimum payments were received. Under Amendment No. 4, for the three and nine months ended September 30, 2025, Air Wisconsin received $0 and $362, respectively, related to the block hour and crew availability minimums. During the three and nine months ended September 30, 2024, Air Wisconsin received $1,420 and $1,904, respectively, related to the block hour and crew availability minimums and estimated that it would receive an additional $14,623 over the remaining term of the American capacity purchase agreement. In accordance with GAAP, the Company recognized revenue related to the total block hour and crew availability minimums on a proportional basis taking into account the number of flights actually completed in the period relative to the number of flights that were expected to be completed in subsequent periods during the remaining term of the agreement. Accordingly, during the three and nine months ended September 30, 2025, Air Wisconsin recognized $— and $2,820 of revenues for block hour and crew availability minimums compared to $3,819 and $3,901 for the three and nine months ended September 30, 2024, respectively. As of September 30, 2025 there were no longer any deferred upfront fee revenues due to the termination of the American capacity purchase agreement in April 2025. As of December 31, 2024, revenues related to the block hour and crew availability minimums in the amounts of $2,458 were netted as part of Contract liabilities, net in the consolidated balance sheets. Air Wisconsin’s block hour and crew availability minimums that were netted as part of Contract liabilities, net on the consolidated balance sheets were adjusted over the remaining contract term, based on the actual revenues that were received and recognized based on the number of flights that were completed in the period relative to the number of flights that were expected to be completed in subsequent periods during the remainder of the term of the agreement. Air Wisconsin received an incentive payment upon the execution of Amendment No. 4. Additionally, Air Wisconsin received an incentive payment related to the wind-down of the American capacity purchase agreement in conjunction with the final payment owed to Air Wisconsin by American following the termination of the American capacity purchase agreement. The Company recognized revenue from such incentive payments proportionately over the departures actually completed and expected to be completed during the remainder of the term of the American capacity purchase agreement. For the three and nine months ended September 30, 2025, the Company recognized $0 and $4,301, respectively, of revenues for such incentive payments. As of September 30, 2025 there were no longer any deferred incentive revenues related to Amendment No. 4 due to the termination of the American capacity purchase agreement in April 2025. As of December 31, 2024, revenues related to the Amendment No. 4 incentive payments in the amount of $3,301 were netted as part of Contract liabilities, net in the consolidated balance sheets and were adjusted over the remaining contract term in proportion to the number of flights completed in the period relative to the number of flights that were expected to be completed over the remaining term of the American capacity purchase agreement. Additionally, Amendment No. 4 modified the total number of aircraft under the American capacity purchase agreement for which Air Wisconsin received a fixed daily amount per aircraft per day (“fixed aircraft payment”) for periods beginning in October 2024 through the end of the term of the American capacity purchase agreement. During the three and nine months ended September 30, 2025, Air Wisconsin received $0 and $9,496, respectively, related to the fixed aircraft payments. In accordance with GAAP, the Company recognized revenue related to the fixed aircraft payments on a proportional basis taking into account the number of flights actually completed in the period relative to the number of flights that were expected to be completed during the remaining term of the American capacity purchase agreement. Accordingly, during the three and nine months ended September 30, 2025, Air Wisconsin recognized $0 and $4,486, respectively, of revenues related to the fixed aircraft payments compared to $0 for the three and nine months ended September 30, 2024. As of September 30, 2025 there were no longer any fixed aircraft payments that were deferred due to the termination of the American capacity purchase agreement in April 2025. As of December 31, 2024, revenues related to the fixed aircraft payments in the amounts of $109 were netted as part of Contract liabilities, net in the consolidated balance sheets. Air Wisconsin’s fixed aircraft payment revenues were netted as part of Contract liabilities, net on the consolidated balance sheets were adjusted over the remaining contract term in proportion to the number of flights that were completed in the period relative to the number of flights that were expected to be completed over the remaining term of the American capacity purchase agreement. During the three and nine months ended September 30, 2025 there were $0 and $4,190, respectively, of revenues recognized that were previously recorded as Contract liabilities, net as of December 31, 2024. For the three and nine months ended September 30, 2024, there were $1,702 and $2,044, respectively, of revenues recognized that were previously recorded as Contract liabilities, net related to the American capacity purchase agreement. On January 3, 2025, American delivered notice to Air Wisconsin of its election to terminate the American capacity purchase agreement. The agreement terminated on April 3, 2025, and contract revenues have not been recorded under that agreement since then. In the fourth quarter of 2024 we began on-demand charter service. Under this service, Air Wisconsin negotiated a fare for the charter operations with the customer where such fare was calculated based on anticipated costs, including fuel and oil, landing fees, passenger screening fees, etc. As many of such costs were estimated, contracts included reconciliation language, however, under some circumstances such costs were borne by Air Wisconsin. For the three and nine months ended September 30, 2025, charter revenues were $528 and $9,333, respectively, representing 58.3% and 14.5%, respectively, of Contract revenues. As of September 30, 2025 and December 31, 2024, the Company had no contract liability outstanding with respect to charter service and had $149 and $635, respectively, recorded as part of Receivables, net on the consolidated balance sheets. There were no credit losses recorded with respect to the charter services during the three and nine months ended September 30, 2025, nor did the Company expect any such credit losses in the future since the expected revenues are deposited in an escrow account prior to any such flights. Contract Assets and Liabilities Contract assets arose from revenue earned for services provided under the American capacity purchase agreement that were not yet billable to American as of the respective dates of the condensed consolidated balance sheets. Contract liabilities arose from payments received in advance of services provided. Contract assets and liabilities that were expected to be settled within the next one-year period were netted in the condensed consolidated balance sheets and included either in Contract assets, net or Contract liabilities, net.
Cash and Cash Equivalents	Cash and Cash Equivalents Money market funds, investments and deposits with an original maturity of three months or less when acquired are considered cash and cash equivalents.
Allowance for Credit Losses	Allowance for Credit Losses The Company monitors publicly available credit ratings for entities for which the Company has a significant credit balance. The Company determined that its receivables, as of September 30, 2025, were primarily the result of its charter operations, insurance-related receivables and income tax refunds. The Company determined that its receivables, as of December 31, 2024, were primarily the result of its relationship with American, charter operations, insurance-related receivables and income tax refunds. These receivables were payable by governmental entities or companies the Company believes to be credit-worthy. Payments for charter services were placed in escrow prior to the flights occurring. Accordingly, the Company has not recorded an allowance for credit losses related to these receivables. The Company maintains an allowance for expected credit losses primarily related to employee receivables.
Marketable Securities, Short-term Restricted Investments (SESP) and Long-term Restricted Investments (SESP)	Marketable Securities, Short-term Restricted Investments (SESP) and Long-term Restricted Investments (SESP) The Company’s equity security investments, consisting of exchange-traded funds and mutual funds, are recorded at fair value based on quoted market prices (Level 1) in Marketable securities, Short-term restricted investments (SESP), and Long-term restricted investments (SESP) in the condensed consolidated balance sheets, in accordance with the guidance in Accounting Standards Codification Topic 321, Investments-Equity Securities, with the change in fair value during the three and nine months ended September 30, 2025 included in the condensed consolidated statements of operations.
Spare Parts and Supplies	Spare Parts and Supplies Spare parts and supplies included an inventory of expendable parts and miscellaneous aircraft supplies stated at average cost less an obsolescence allowance. The Company provided for an allowance for obsolescence after considering a number of factors, including the useful life of the aircraft fleet, the estimated cost of expendable parts expected to be on hand at the end of the useful life and the estimated salvage value of the parts. This allowance was based on management estimates and was subject to change. Expendable parts were charged to expense at average cost when used. Expendable parts that were repairable were returned to inventory at the average cost of comparable parts, less a reserve for scrap. Supplies were stated at average cost. The inventory allowance was $17,097 and $17,120 as of September 30, 2025 and December 31, 2024, respectively. The Company, from time to time, consigned certain of its spare parts and supplies to third parties for sale. Title of any such parts or supplies remained with the Company until a sale was made. To the extent the Company did consign any such spare parts and supplies, it was not material to its inventory. The Company viewed the net carrying value of any consigned spare parts and supplies to be $0 for all periods presented due to its obsolescence reserve.
Contract Costs	Contract Costs Contract costs arose from the incremental costs incurred by Air Wisconsin to fulfill its obligations under the American capacity purchase agreement and included costs such as aircraft painting and aircraft reconfiguration. Contract costs were amortized under the capacity purchase agreement based on the completion of Air Wisconsin's performance obligation as measured by departures. Air Wisconsin incurred certain contract costs (“fulfillment costs”) prior to the start of flying operations for American on March 1, 2023. These costs included changes to the livery, fuel costs, and certain training expenses. The total fulfillment costs incurred as of September 30, 2025 and December 31, 2024 were $774. These costs were amortized on a proportional basis taking into account the number of flights actually completed in the period relative to the number of flights expected to be completed in subsequent periods during the remaining term of the agreement. Those contract costs that were expected to be amortized over the next one-year period were included in Contract costs in the condensed consolidated balance sheets.
Impairment of Long-Lived Assets and Indefinite-Lived Intangible Assets	Impairment of Long-Lived Assets and Indefinite-Lived Intangible Assets The Company evaluates long-lived assets and indefinite-lived intangible assets for potential impairment and records impairment losses when events and circumstances indicate the assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than their carrying amounts. When considering whether an impairment of long-lived assets exists, the Company is required to group similar assets together at the lowest level for which identifiable cash flows for such assets are largely independent of the cash flows of other assets and liabilities. The Company determined that because there is only one operating segment, similar revenue contracts each resulting from airline operations, and one aircraft type, the asset group was at the enterprise level and as such, performed an assessment of all assets and liabilities of the Company. The Company determined that indicators of impairment existed cumulatively through the twelve months ended December 31, 2024 and thus performed a quantitative test for impairment. Based on an analysis of the fair market value of its assets, the Company determined that an impairment charge was not required as of December 31, 2024. The Company determined that the same indicators of impairment that existed during the twelve months ended December 31, 2024 continued to exist with respect to its long-lived assets during the three and nine months ended September 30, 2025, requiring the Company to perform a quantitative test for impairment. The accounting guidance provides examples of events that may indicate a long-lived asset group may not be recoverable. The relevant examples include a significant adverse change in the extent or manner in which a long-lived asset is used, a significant adverse change in the business climate that could affect the value of a long-lived asset group, or a current period operating or cash flow loss. The Company determined these indicators of impairment continued to be applicable over the three and nine months ended September 30, 2025, primarily as a result of the termination of the American capacity purchase agreement on April 3, 2025, combined with the negative trends in prior periods related to lower aircraft usage and operating and cash flow losses existing as of December 31, 2024. However, based on an analysis of the fair market value of its long-lived assets, the Company determined that an impairment charge was not required as of September 30, 2025. The Company further concluded that its indefinite lived intangible assets continued to be indefinite lived intangible assets as of September 30, 2025 and that its intangible assets should be evaluated as one unit of account for determining impairment. Although indicators of impairment existed as of September 30, 2025 with respect to the intangible assets, the Company concluded, based on a qualitative assessment weighing the positive and negative evidence, that the significant inputs used to determine the fair value of the indefinite-lived intangible assets were not materially changed as of September 30, 2025. As a result, the Company determined that the indefinite-lived intangible assets were not impaired. Although the Company continued to monitor for impairment as a result of the termination of the American capacity purchase agreement in on April 3, 2025, the sale of certain assets in 2025 and the completion of the Aviation Disposition provided further validation that an impairment charge was not necessary.
Supplemental Executive Savings Plan ("SESP")	Supplemental Executive Savings Plan (“SESP”) The Company maintained the SESP for the benefit of certain executives. The SESP offered deferred compensation retirement benefits that would otherwise be subject to the compensation limits imposed by the Internal Revenue Code on Company contributions to the Air Wisconsin Airlines Savings Plan. At the end of each year, the Company accrued a long-term deferred compensation liability for contributions earned during that year that were contributed to the SESP in January of the successive year. Assets acquired within the plan were recorded as Long-term restricted investments (SESP) and an offsetting liability was recorded as Long-term deferred compensation (SESP) in the condensed consolidated balance sheets. Due to the resignation of certain employees, a portion of the SESP assets and liabilities have been classified as short-term as of September 30, 2025. Any increases or decreases in plan assets due to changes in market value were recorded as a Gain on Marketable securities, Short-term restricted investments (SESP), and Long-term restricted investments (SESP), with an offsetting entry made to Payroll and related costs in the condensed consolidated statements of operations. This results in no impact on net income before taxes. The values of Short-term restricted investments (SESP), Long-term restricted investments (SESP), Short-term deferred compensation (SESP) liability, and Long-term deferred compensation (SESP) liability associated with the SESP were adjusted quarterly to reflect changes in market value.
Other Assets	Other Assets Other non-current assets consist of expected amounts to be received in future periods at least one-year beyond the respective dates of the condensed consolidated balance sheets.
Interest and Dividend Income	Interest and Dividend Income The Company records investment income earned on its cash equivalents and marketable securities, consisting primarily of interest and dividends, in Interest and dividend income in the condensed consolidated statements of operations.
Income Taxes	Income Taxes The Company utilizes the asset and liability method for accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based upon the estimated future tax effects of differences between the financial statement and tax basis of assets and liabilities, as measured by the current applicable tax rates. Deferred tax expense represents the result of changes in deferred tax assets and liabilities. Determining whether deferred tax assets are impaired requires significant judgment, including but not limited to, forecasting the reversal of temporary differences. A valuation allowance is provided for those deferred tax assets for which the Company cannot conclude that it is more likely than not that such deferred tax assets will be realized. In determining the amount of any valuation allowance, in addition to the reversal of temporary differences, estimated future taxable income as well as feasible tax planning strategies for each taxing jurisdiction, are considered. Each fiscal quarter the Company reevaluates its tax provision and reconsiders the estimates and assumptions related to specific tax assets and liabilities, making adjustments as circumstances change. As required by the uncertain tax position guidance, the Company recognizes the financial statement benefit of a tax position only after determining that the relevant tax authority would more-likely-than-not sustain the position following an audit. For tax positions meeting the more-likely-than-not threshold, the amount recognized in the condensed consolidated financial statements is the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement with the relevant tax authority. The Company has applied the uncertain tax position guidance to all tax positions for which the statute of limitations remains open. The Company is subject to federal, state and local income taxes in the United States. Tax regulations within each jurisdiction are subject to the interpretation of the related tax laws and regulations and require the application of significant judgment. The Company is no longer subject to U.S. federal income tax examinations for the years prior to 2021. With a few exceptions, the Company is no longer subject to state or local income tax examinations for years prior to 2020. As of September 30, 2025, the Company had no outstanding tax examinations except for the routine review of the Company's 2022 amended federal income tax return by the Internal Revenue Service and the Joint Committee on taxation.
Concentration of Credit Risk and Customer Risk	Concentration of Credit Risk and Customer Risk Financial instruments that potentially expose the Company to a concentration of credit risk consist principally of cash and cash equivalents that are held by financial institutions in the United States and accounts receivable. The Company at times has had bank deposits in excess of the Federal Deposit Insurance Corporation insurance limit. The Company maintains its cash accounts with high credit quality financial institutions and, accordingly, the Company believes it has minimal credit risk with respect to these financial institutions. As of September 30, 2025 and December 31, 2024, in addition to cash and cash equivalents of $17,241 and $14,952, respectively, the Company had $589 and $667, respectively, in restricted cash, which related to a credit facility used for the issuance of cash collateralized letters of credit supporting Air Wisconsin's obligations under certain lease agreements, airport agreements and insurance policies, as well as cash held for the repurchase of shares under Harbor’s stock repurchase program. Restricted cash includes amounts escrowed in an interest-bearing account that secures the credit facility. Air Wisconsin's obligations supported by these letters of credit remained with Air Wisconsin following the Aviation Disposition. Air Wisconsin has historically faced considerable customer concentration of risk. Significant customers are those which represent more than 10% of the Company’s total revenue or net accounts receivable balance at each respective balance sheet date. Approximately —% and 84.9% of the Company's consolidated revenues for the three and nine months ended September 30, 2025 were derived from the American capacity purchase agreement compared to approximately 100.0% for the both the three and nine months ended September 30, 2024. As of September 30, 2025, none of the Receivables, net balance in the consolidated balance sheets was derived from the American capacity purchase agreement compared to 46.0% as of December 31, 2024. The American capacity purchase agreement terminated effective April 3, 2025. In the fourth quarter of 2024, Air Wisconsin began on demand charter service. Although certain of its customers represented more than 10% of the Company's total revenue during the three and nine months ended September 30, 2025, all payments due to Air Wisconsin were pre-paid and held in escrow until completion of the flights. American's obligations to pay Air Wisconsin the amounts required to be paid under the American capacity purchase agreement were not collateralized. For additional information, please refer to Note 2, Capacity Purchase Agreement with American.
Estimates and Assumptions	Estimates and Assumptions The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. The most significant estimates relate to revenue recognition, long-lived assets, and income taxes. Management evaluates its estimates and assumptions on an ongoing basis using historical experience, existing and known circumstances, authoritative accounting guidance, and other factors management believes to be reasonable, including an assessment of current and anticipated future macroeconomic conditions, and makes adjustments when facts and circumstances dictate. These estimates are based on information available as of the date of the financial statements. To the extent there are differences between these estimated and actual results, it may result in material effects on the Company’s financial condition, results of operations and liquidity.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments include Cash and cash equivalents, Restricted cash, Marketable securities, Short-term restricted investments (SESP), Long-term restricted investments (SESP), Receivables, net, Long-term investments, Accounts payable, and Long-term promissory note. The Company believes the carrying amounts of these financial instruments, with the exception of Marketable securities, Short-term restricted investments (SESP), and Long-term restricted investments (SESP), are a reasonable estimate of their fair value because of the short-term nature of such instruments, or, in the case of the Long-term promissory note, because the Company also holds the promissory note evidencing such obligation, which is reflected in Long-term investments on the consolidated balance sheets. Marketable securities, Short-term restricted investments (SESP), and Long-term restricted investments (SESP) are reported at fair value based on quoted market prices. Long-term investments are held-to-maturity debt securities and are reported at amortized cost. For additional information regarding the Long-term promissory note and Long-term investments, please refer to Note 4, Debt. Fair value is defined as the price that would be received to sell an asset, or paid to transfer a liability, in an orderly transaction between market participants at the measurement date, which is otherwise referred to as an exit price. Accounting Standards Codification Topic 820, Fair Value Measurement (“ASC 820”) establishes a three-tier fair value hierarchy, which prioritizes inputs used in fair value. The tiers are as follows: Level 1 - Quoted market prices in active markets for identical assets or liabilities. Level 2 - Inputs other than Level 1 inputs that are either directly or indirectly observable. Level 3 - Unobservable inputs developed using the Company’s estimates and assumptions, which reflect those that market participants would use. The determination of where an asset or liability falls in the hierarchy requires significant judgment. The Company evaluates these determinations each reporting period, and it is possible that an asset or liability may be classified differently from year to year.
Reclassifications	Reclassifications Gains on the sale of fixed assets previously recorded in Purchased services and other in the consolidated statements of operations in the amounts of $3 and $519 for the three and nine months ended September 30, 2024, respectively, have been reclassified to Gains on the sale of fixed assets to conform to the presentation for the three and nine months ended September 30, 2025, with no effect on net income.
Recently Adopted and Upcoming Accounting Pronouncements	Recently Adopted Accounting Pronouncement On January 1, 2024 the Company adopted the updates to ASU No. 2023-07, Segment Reporting (ASC Topic 280) – Improvements to Reportable Segment Disclosures. These updates are intended to improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses, with the intention of enabling users of the financial statements to better understand the entity's measurement and assessment of segment performance and resource allocation. Upon adoption the guidance was applied retrospectively to all periods presented. Beyond enhanced disclosures, the adoption of this standard did not have an impact on the Company's consolidated financial statements. Upcoming Accounting Pronouncements In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (ASC Topic740) – Improvements to Income Tax Disclosures (“ASC 740”), which is intended to enhance the transparency, effectiveness and comparability of income tax disclosures by requiring consistent categories and greater disaggregation of information related to income tax rate reconciliations and the jurisdictions in which income taxes are paid. The guidance is effective for annual periods beginning after December 15, 2024, with early adoption permitted. While the Company expects expanded disclosures in its Annual Report on Form 10-K for the year ended December 31, 2025, it continues to evaluate the impact of adopting this new guidance on its consolidated financial statements and related disclosures. The Company does not plan to adopt ASU No. 2023-09 early. In March 2024, the FASB issued ASU No. 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (ASC Subtopic 220-40) – Disaggregation of Income Statement Expenses, which enhances the transparency and comparability of financial statements by requiring companies to disclose more granular information about expense components. As clarified in ASU 2025-01, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Clarifying the effective date, the guidance is effective for annual periods beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the potential impact of adopting this new guidance on its consolidated financial statements and related disclosures.

HARBOR DIVERSIFIED, INC. 10-Q