Frontier's letter described the strategic rationale as creating "the country's first, at-scale, low-fare carrier," stating the combined airline would be the fifth largest in the United States, growing to 100 million annual passengers and more than 400 aircraft within a few years, and a top-three carrier at more than half of the top 25 U.S. airports. Frontier's January 28, 2025 presentation to Spirit argued the combination would create "America's first low-cost carrier with sufficient scale to compete with the Big Four."

Under the terms of the Proposal, Spirit's stakeholders (senior secured noteholders, convertible noteholders and existing equity interests) would have received $400 million principal amount of new debt issued by Frontier plus 19.0% of Frontier's common equity, which Frontier valued at an aggregate of no less than $2,162 million before synergies, rising to as much as $2,901 million including an assumed $600 million of run-rate synergies. Frontier calculated this against a pro forma combined enterprise value of $18,630 million (applying the 6.5x 2026E EBITDAR multiple used in Spirit's own plan) less pro forma net debt of $9,356 million as of February 28, 2025, implying combined equity value of $9,274 million. Frontier said it had engaged a management consulting firm with aviation expertise that estimated potential revenue synergies of $500 million or more and cost synergies of $100 million or more, together underpinning its assumed $600 million synergy figure, with no phase-in timeline disclosed. The Proposal also required Spirit's consenting creditors to fund a previously announced $350 million equity rights offering, with proceeds used to retire Spirit's debtor-in-possession financing.

Frontier's letter disclosed that it had retained Citigroup Global Markets Inc. as financial advisor and Latham & Watkins LLP as legal counsel for the proposal. Spirit's 8-K stated only that its management and board reviewed the proposal "in consultation with the Company's external legal and financial advisors," without naming them in the filed exhibits reviewed.

Spirit's board and the advisors to its senior secured noteholders and convertible noteholders rejected the Proposal. In its January 11, 2025 response (Exhibit 99.2), Spirit noted that Frontier's new terms were a material reduction from an agreement in principle reached in the summer and fall of 2024 that would have given Spirit stakeholders 26.5% of the combined company's equity and $580 million of take-back debt, versus the $400 million of debt and 19% equity now proposed, while still requiring creditors to fund a new $350 million equity investment. Spirit's January 29, 2025 Form 8-K disclosed that the company and the noteholder advisors concluded the Proposal "would deliver less in value to the Company's stakeholders than what was contemplated by the Company's existing Plan, is uncertain as to timing and completion, including the need for regulatory and court approvals, and is not actionable considering it would require the NDA Parties to invest $350 million in equity, which they were not willing to do." The filing also noted that, unless waived, the Proposal would have triggered a $35 million break-up fee under Spirit's court-approved equity rights offering backstop agreement. In its final letter to Frontier dated January 28, 2025 (Exhibit 99.8), Spirit stated its board "concluded that continuing to delay our confirmation and emergence process carries too many risks for the Company and its stakeholders and would be irresponsible," and noted its bondholder groups had declined to extend the related non-disclosure agreements.

Spirit proceeded with its original, standalone pre-arranged Chapter 11 plan rather than Frontier's proposal. The Bankruptcy Court entered an order confirming that plan on February 20, 2025, and the plan became effective on March 12, 2025, at which point Spirit Aviation Holdings, Inc. became the new parent company of the reorganized airline (per Spirit's Form 8-K15D5 filed March 13, 2025). No subsequent SEC filing by Spirit references a revived Frontier proposal or any Frontier transaction. Based on the filings reviewed, the Frontier proposal to acquire Spirit was rejected and did not proceed; it was not a pending, signed, or regulatory-approval-stage transaction.