UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 29, 2011

SPIRIT AIRLINES, INC.

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation)

2800 Executive Way

Miramar, Florida 33025

(Address of principal executive offices, including Zip Code)

(954) 447-7920

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

The information in this report furnished pursuant to Items 2.02 and 7.01 shall not be deemed “filed” for the purposes of Section 18 of the Securities and Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. It may only be incorporated by reference in another filing under the Exchange Act or the Securities Act of 1933, as amended, if such subsequent filing specifically references the information furnished pursuant to Items 2.02 and 7.01 of this report.

Spirit Airlines, Inc. (the “Company” or “Spirit”) is providing below the following supplemental financial information to facilitate further analysis of its financial results:

This data should be read in conjunction with our historical audited financial statements, Management’s Discussion and Analysis of Financial Condition and Results of Operations and other information included in the Final Prospectus, as well as the information provided under the caption “Forward Looking Statements” below. A copy of the Final Prospectus may be obtained by accessing the Edgar database maintained by the Securities and Exchange Commission at www.sec.gov.

The financial data provided herein that reflects adjustments from historical financial data prepared under GAAP, including adjustments for special items and for pro forma calculations assuming our IPO had been completed as of an earlier date than it was actually completed, are non-GAAP financial measures included as supplemental disclosures because we believe they are useful indicators of our operating performance for comparative purposes. These non-GAAP financial measures are well recognized performance measurements in the airline industry that are frequently used by investors, securities analysts and other interested parties in comparing the operating performance of

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companies in our industry. These non-GAAP financial measures have limitations as an analytical tool. Because of these limitations, determinations of our operating performance adjusted for special items and pro forma for our IPO should not be considered in isolation or as a substitute for performance measures calculated in accordance with GAAP. We have also provided reconciliations of these non-GAAP financial measures to the appropriate GAAP financial measures.

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Statement of Operations Data- GAAP (1)

(Unaudited)

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Reconciliation of Operating Expenses and Net Income as Adjusted for Special Items

(Unaudited)

Note: Additional detail regarding the foregoing adjustments is available on page 77 of the Final Prospectus.

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Reconciliation of Pro Forma Adjustments (1)

(Unaudited)

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Selected Operating Metrics

(Unaudited)

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Selected Financial Guidance

Forward-Looking Statements

This report includes forward-looking statements, including in particular as provided under the caption “Selected Financial Guidance.” We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends affecting the financial condition of our business. Forward-looking statements should not be read as a guarantee of future performance or results, and will not necessarily be accurate indications of the times at, or by, which such performance or results will be achieved. Forward-looking statements are based on information available at the time those statements are made and/or management’s belief as of that time with respect to future events, and are subject to risks and uncertainties that could cause actual performance or results to differ materially from those expressed in or suggested by the forward-looking statements, including the information under the caption “Risk Factors” included in the Final Prospectus. Important factors that could cause such differences include, but are not limited to:

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In addition, in this report, the words “believe,” “may,” “estimate,” “continue,” “anticipate,” “intend,” “expect,” “predict,” “potential” and similar expressions, as they relate to our company, our business and our management, are intended to identify forward-looking statements. In light of these risks and uncertainties, the forward-looking events and circumstances discussed in this report may not occur and actual results could differ materially from those anticipated or implied in the forward-looking statements.

All forward-looking statements attributable to us are expressly qualified in their entirety by the cautionary statements set forth above. Forward-looking statements speak only as of the date of this report. You should not put undue reliance on any forward-looking statements. We assume no obligation to update forward-looking statements to reflect actual results, changes in assumptions or changes in other factors affecting forward-looking information, except to the extent required by applicable law. If we update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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