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): December 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:

On December 29, 2011, Spirit Airlines, Inc. (the “Company”) entered into Amendment No. 11 to the Airbus A320 Family Purchase Agreement, by and between the Company and Airbus S.A.S. (legal successor to AVSA S.A.R.L.) (“Airbus”), dated as of May 5, 2004, and eight separate letter agreements related thereto (as amended and supplemented to date by such letter agreements thereto, the “Airbus Amendment”). The Airbus Amendment represents the definitive agreement memorializing the Memorandum of Understanding, previously announced on November 15, 2011, for an order of 75 A320 family aircraft consisting of 30 of the existing aircraft model and 45 A320 NEO (New Engine Option) aircraft. These aircraft are scheduled for delivery from 2016 through 2021 and are in addition to the 31 aircraft scheduled to be delivered under the Company’s existing order from 2012 through 2015.

The foregoing description does not purport to be complete and is qualified in its entirety by reference to the Airbus Amendment, a copy of which is filed as Exhibit 10.1 attached hereto, and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

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.

EXHIBIT INDEX