Current Developments	9 Months Ended
Current Developments	Sep. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Current Developments	Current Developments Termination of JetBlue Merger On July 28, 2022, Spirit entered into an Agreement and Plan of Merger (the “Merger Agreement”) with JetBlue Airways Corporation, a Delaware corporation (“JetBlue”), and Sundown Acquisition Corp., a Delaware corporation and a direct, wholly owned subsidiary of JetBlue (“Merger Sub”), pursuant to which and subject to the terms and conditions therein, Merger Sub would have merged with and into Spirit, with Spirit continuing as the surviving entity (the “Merger”). In accordance with the terms of the Merger Agreement, on October 26, 2022, JetBlue paid the Spirit stockholders an approval prepayment amount (the "Approval Prepayment Amount") of $2.50 per share. Additionally, beginning January 2023, and through the termination of the Merger Agreement on March 1, 2024, JetBlue paid on a monthly basis additional prepayments (the "Additional Prepayments") of $0.10 per share of common stock to all Spirit stockholders of record. Due to the payment of the Approval Prepayment Amount and each of the Additional Prepayment Amounts, in accordance with the terms of the respective debt indentures and warrant agreements, the Company announced related adjustments to the conversion rates of its 4.75% convertible senior notes due 2025 (“convertible notes due 2025”) and its 1.00% convertible senior notes due 2026 (“convertible notes due 2026” and, collectively with the convertible notes due 2025, the “convertible notes”), as well as adjustments to the exercise prices and warrant shares of the PSP1, PSP2 and PSP3 warrants outstanding. On March 1, 2024, Spirit, JetBlue and Merger Sub entered into a Termination Agreement (the “Termination Agreement”), pursuant to which the Merger Agreement was terminated, effective immediately. JetBlue ceased paying Additional Prepayment Amounts and, therefore, no further adjustments to the conversion rates of the Company's convertible notes due 2025 and convertible notes due 2026 or to the exercise prices and warrant shares of the PSP1, PSP2 and PSP3 warrants outstanding were made in connection with the Merger Agreement. As of September 30, 2024, the conversion rates of the convertible notes due 2025 and 2026 were 97.5929 and 25.3578 shares of voting common stock per $1,000 principal amount of convertible notes, respectively. In addition, as of September 30, 2024, the exercise prices of the PSP1, PSP2 and PSP3 warrants were $11.393, $19.761 and $29.496, respectively and the number of warrant shares issuable upon the exercise of the PSP1, PSP2 and PSP3 warrants were adjusted to 643,625.20, 170,230.67 and 99,526.95, respectively. In addition, under the terms of the Termination Agreement, JetBlue paid the Company $69.0 million in cash, of which $66.7 million was recorded in other (income) expense within the Company's condensed consolidated statements of operations. The remaining $2.3 million was recorded as a reduction in accounts receivable, net within the Company's condensed consolidated balance sheets related to the amounts owed by JetBlue. Pratt & Whitney On July 25, 2023, RTX Corporation, parent company of Pratt & Whitney, announced that it had determined that a rare condition in the powdered metal used to manufacture certain engine parts will require accelerated inspection of the PW 1100G-JM geared turbo fan (“GTF”) fleet, which powers the Company's A320neo family of aircraft. The temporary removal of engines from service has driven and is expected to continue contributing to a significant decrease in the Company's growth projections. The Company has reduced capacity in amounts and timing commensurate with the currently scheduled removal and inspection of these impacted engines, however, the Company continues to assess the impact on its future capacity plans. On March 26, 2024, the Company entered into an agreement (the “Agreement”) with International Aero Engines, LLC ("IAE"), an affiliate of Pratt & Whitney, pursuant to which IAE will provide the Company with a monthly credit, subject to certain conditions, as compensation for each of the Company's aircraft unavailable for operational service due to GTF engine issues from October 1, 2023 through the end of 2024. The credits are accounted for as vendor consideration in accordance with ASC 705-20 and are recognized as a reduction of the purchase price of the goods or services acquired from IAE during the period, which may include the purchase of maintenance, spare engines and short-term rentals of spare engines, based on an allocation that corresponds to the Company’s progress towards earning the credits. Pratt & Whitney agreed to issue the Company $116.9 million in credits related to the aircraft on ground ("AOG") days through September 30, 2024. During the three and nine months ended September 30, 2024, the Company recognized $29.7 million and $104.7 million, respectively. Of the amounts recognized, as of September 30, 2024, the Company had recorded $92.6 million of credits as a reduction in the cost basis of assets purchased from IAE within flight equipment and deferred heavy maintenance, net on the Company's condensed consolidated balance sheets. During the three and nine months ended September 30, 2024, the Company recorded $4.9 million and $12.1 million of these credits, respectively, on the Company's condensed consolidated statements of operations within maintenance, materials and repairs and aircraft rent. In addition, during the three and nine months ended September 30, 2024, the Company recognized lower depreciation expense of $3.9 million and $5.5 million, respectively, related to credits recognized as a reduction of the cost basis of assets purchased from IAE in depreciation and amortization within the Company's condensed consolidated statements of operations. The difference remaining between the amount of credits Pratt & Whitney agreed to issue and the amount the Company has recognized will be recognized in the future as reductions in the cost basis of goods and services purchased from Pratt & Whitney. The temporary removal of engines from service is expected to continue through at least 2026. The Company is currently discussing arrangements with Pratt & Whitney for any of its aircraft that remain unavailable for operational service after December 31, 2024.