FORM OF LETTER OF TRANSMITTAL OFFER TO EXCHANGE OUTSTANDING SHARES OF COMMON STOCK

Exhibit 99.1

Letter of Transmittal

To Offer to Exchange Each Outstanding Share of Common Stock

(Including the Associated Preferred Stock Purchase Rights)

of

MIDWEST AIR GROUP, INC.

for $13.25 consisting of

$6.6250 in Cash and

0.5884 of a Share of AirTran Holdings, Inc. Common Stock

by

Galena Acquisition Corp., a wholly owned subsidiary of

AIRTRAN HOLDINGS, INC.

Pursuant to the Prospectus dated January 11, 2007

THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON THURSDAY, FEBRUARY 8, 2007, UNLESS THE OFFER IS EXTENDED. SECURITIES TENDERED PURSUANT TO THE OFFER MAY BE WITHDRAWN AT ANY TIME PRIOR TO THE EXPIRATION DATE, BUT NOT DURING ANY SUBSEQUENT OFFERING PERIOD.

The exchange agent for the offer is:

The Bank of New York

DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS, OR TRANSMISSION OF INSTRUCTIONS VIA A FACSIMILE NUMBER, OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID DELIVERY.

THE PROSPECTUS INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.

This Letter of Transmittal is to be used if certificates are to be forwarded herewith or, unless an agent’s message (as defined in the Prospectus) is utilized, if delivery of Midwest Shares (as defined below) is to be made by book-entry transfer to the Exchange Agent’s account at The Depository Trust Company (the “Book-Entry Transfer Facility”) pursuant to the procedures set forth under in the Prospectus under the caption “The Offer—Procedure for Tendering.”

IF ANY OF THE CERTIFICATES REPRESENTING SHARES THAT YOU OWN HAVE BEEN LOST OR DESTROYED, SEE INSTRUCTION 9 OF THIS LETTER OF TRANSMITTAL.

Holders of outstanding shares of common stock (the “Midwest Shares”) of Midwest Air Group, Inc. (“Midwest”) whose certificates for such Midwest Shares (the “Share Certificates”) are not immediately available or who cannot deliver their Share Certificates and all other required documents to the Exchange Agent on or prior to the expiration date (as defined in the Prospectus), or who cannot complete the procedure for book-entry transfer on a timely basis, must tender their Midwest Shares according to the guaranteed delivery procedure set forth in the Prospectus under the caption “The Offer—Guaranteed Delivery.” See Instruction 2. Delivery of documents to the Book-Entry Transfer Facility does not constitute delivery to the Exchange Agent.

LOST CERTIFICATES

TENDER OF SHARES

NOTE: SIGNATURES MUST BE PROVIDED BELOW.

PLEASE READ ACCOMPANYING INSTRUCTIONS CAREFULLY.

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Ladies and Gentlemen:

The undersigned hereby tenders to Galena Acquisition Corp. (“Galena”), a Delaware corporation and wholly owned subsidiary of AirTran Holdings, Inc., a Nevada corporation (“AirTran”), the above-described shares of common stock, together with the Series A Junior Participating Preferred Stock Purchase Rights (the “Midwest Shares”), of Midwest Air Group, Inc. (“Midwest”), pursuant to Galena’s offer to exchange $13.25 in value, consisting of $6.6250 in cash, without interest, and 0.5884 of a share of common stock, par value $0.001 per share, of AirTran (“AirTran Shares”) for each outstanding Midwest Share, upon the terms and subject to the conditions set forth in the Prospectus, dated January 11, 2007 (the “Prospectus”), receipt of which is hereby acknowledged, and in this Letter of Transmittal (which together, as each may be amended, supplemented or otherwise modified from time to time, constitute the “Offer”). The undersigned understands that Galena reserves the right to transfer or assign, in whole or from time to time in part, to one or more of its affiliates the right to purchase Midwest Shares tendered pursuant to the Offer, but any such transfer or assignment will not relieve Galena of its obligations under the Offer or prejudice the undersigned’s rights to receive AirTran Shares and cash for Midwest Shares validly tendered and accepted for exchange.

Upon the terms and subject to the conditions of the Offer and effective upon acceptance of the Midwest Shares tendered herewith in accordance with the terms of the Offer, the undersigned hereby sells, assigns and transfers to, or upon the order of, Galena all right, title and interest in and to all of the Midwest Shares that are being tendered hereby (and any and all dividends, distributions, rights, other Midwest Shares or other securities issued or issuable in respect thereof on or after the date hereof (collectively, a “Distribution”)) and appoints the Exchange Agent the true and lawful agent and attorney-in-fact of the undersigned with respect to such Midwest Shares (and any Distribution), with full power of substitution (such power of attorney being deemed to be an irrevocable power coupled with an interest), to (i) deliver certificates for such Midwest Shares (and any Distribution), or transfer ownership of such Midwest Shares (and any Distribution) on the account books maintained by the Book-Entry Transfer Facility, together, in any such case, with all accompanying evidences of transfer and authenticity, to or upon the order of Galena, (ii) present such Midwest Shares (and any Distribution) for transfer on the books of Midwest, and (iii) receive all benefits and otherwise exercise all rights of beneficial ownership of such Midwest Shares (and any Distribution), all in accordance with the terms of the Offer.

The undersigned hereby irrevocably appoints designees of Galena as the attorneys and proxies of the undersigned, each with full power of substitution, to exercise all voting and other rights of the undersigned in such manner as each such attorney and proxy or his substitute shall in his sole discretion deem proper, with respect to all of the Midwest Shares tendered hereby which have been accepted for exchange by Galena prior to the time of any vote or other action (and any Distribution), at any meeting of shareholders of Midwest (whether annual or special and whether or not an adjourned meeting), by written consent or otherwise. This proxy is irrevocable and is granted in consideration of, and is effective upon, the acceptance for exchange of such Midwest Shares by Galena in accordance with the terms of the Offer. Such acceptance for exchange shall revoke any other proxy or written consent granted by the undersigned at any time with respect to such Midwest Shares (and any Distribution), and no subsequent proxies will be given or written consents will be executed by the undersigned (and if given or executed, will not be deemed to be effective).

The undersigned hereby represents and warrants that the undersigned has full power and authority to tender, sell, assign and transfer the Midwest Shares tendered hereby (and any Distribution) and that when the same are accepted for exchange by Galena, Galena will acquire good and unencumbered title thereto, free and clear of all liens, restrictions, charges and encumbrances and not subject to any adverse claims. The undersigned will, upon request, execute and deliver any additional documents deemed by the Exchange Agent or Galena to be necessary or desirable to complete the sale, assignment and transfer of the Midwest Shares tendered hereby (and any Distribution).

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All authority herein conferred or agreed to be conferred shall survive the death or incapacity of the undersigned, and any obligation of the undersigned hereunder shall be binding upon the heirs, personal representatives, successors and assigns of the undersigned. Except as stated in the Offer, this tender is irrevocable.

The undersigned understands that tenders of Midwest Shares pursuant to any one of the procedures described in the Prospectus under the caption “The Offer—Procedure for Tendering” and in the instructions hereto will constitute a binding agreement between the undersigned, Galena upon the terms and subject to the conditions of the Offer. The undersigned recognizes that under certain circumstances set forth in the Prospectus, Galena may not be required to accept for exchange any of the Midwest Shares tendered hereby.

The undersigned understands that the delivery and surrender of Midwest Shares that the undersigned has tendered is not effective, and the risk of loss of Midwest Shares does not pass to the Exchange Agent, until the Exchange Agent receives the Letter of Transmittal, duly completed and signed, or an agent’s message (as discussed in the Prospectus in the section entitled “The Offer—Procedure for Tendering”) in connection with a book-entry transfer of shares, together with all accompanying evidences of authority in form satisfactory to Galena and any other required documents. THE UNDERSIGNED UNDERSTANDS THAT ALL QUESTIONS AS TO THE FORM OF DOCUMENTS (INCLUDING NOTICES OF WITHDRAWAL) AND THE VALIDITY, FORM, ELIGIBILITY (INCLUDING TIME OF RECEIPT) AND ACCEPTANCE FOR EXCHANGE OF ANY TENDER OF MIDWEST SHARES WILL BE DETERMINED BY GALENA AND IN ITS SOLE DISCRETION AND SUCH DETERMINATION SHALL BE FINAL AND BINDING UPON ALL TENDERING MIDWEST SHAREHOLDERS. The undersigned also understands that no tender of Midwest Shares is valid until all defects and irregularities in tenders of Midwest Shares have been cured or waived and that none of Galena, AirTran or the Exchange Agent, the information agent, the dealer managers or any other person is under any duty to give notification of any defects or irregularities in the tender of any Midwest Shares or will incur any liability for failure to give any such notification.

Unless otherwise indicated under “Special Issuance Instructions,” please issue the AirTran Shares and a check for cash (including any cash in lieu of fractional AirTran Shares), and return any Midwest Shares not tendered or not accepted for exchange, in the name(s) of the undersigned (and, in the case of Midwest Shares tendered by book-entry transfer, by credit to the account at the Book-Entry Transfer Facility). Similarly, unless otherwise indicated under “Special Delivery Instructions,” please mail the AirTran Shares and a check for cash (including any cash in lieu of fractional AirTran Shares) and any certificates for Midwest Shares not tendered or not accepted for exchange (and accompanying documents, as appropriate) to the undersigned at the address shown below the undersigned’s signature(s). In the event that both “Special Issuance Instructions” and “Special Delivery Instructions” are completed, please issue the AirTran Shares and a check for cash (including any cash in lieu of fractional AirTran Shares) and return any Midwest Shares not tendered or not accepted for exchange in the name(s) of, and mail said check and any certificates to, the person(s) so indicated. The undersigned recognizes that Galena has no obligation, pursuant to the “Special Issuance Instructions,” to transfer any Midwest Shares from the name of the registered holder(s) thereof if Galena does not accept for exchange any of the Midwest Shares so tendered.

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