AIRTRAN HOLDINGS PROPOSES MERGER WITH MIDWEST AIR GROUP

Exhibit 99.1

AIRTRAN HOLDINGS PROPOSES MERGER WITH MIDWEST AIR GROUP

—Transaction Premium of 37% at Time of Offer—

—Plan Would Create National Low-Cost Carrier with a Broad Network, Strong Fleet Commonality and Shared Corporate Culture—

—Combination Will Provide Enhanced Growth and Security for Midwest Shareholders, Employees, Customers and Communities Served—

—More than $60 Million of Estimated Annual Synergies—

ORLANDO, Fla., December 13, 2006 – AirTran Holdings, Inc. (NYSE: AAI), the parent of AirTran Airways, announced today it has made a proposal to acquire all of the outstanding common stock of Midwest Air Group, Inc. (AMEX: MEH) for $11.25 per Midwest share in cash and AirTran stock or a total equity value of approximately $290 million. The offer represents a 37% premium to the thirty day average closing price and an 89% premium to the six months average closing price for Midwest’s common stock, prior to October 20, 2006, the date the offer was made.

The proposed merger was initially outlined in a letter from Joe Leonard, Chairman and Chief Executive Officer of AirTran Holdings, to the Midwest Board of Directors on October 20, 2006. After a series of communications between the principals and the companies’ respective advisors, on December 7, 2006, Mr. Leonard was informed that the Midwest board had declined AirTran’s merger offer, determined not to consider AirTran’s proposal further and intended to remain independent. Today, Mr. Leonard sent a letter to the Midwest board advising them that AirTran would continue to pursue a merger with Midwest because it believes the proposed combination offers substantial and compelling benefits to the constituents of both Midwest Airlines and AirTran Airways. (Both letters are attached below.)

The combination of AirTran Airways and Midwest Airlines would create a truly national low cost airline with pro forma revenue of approximately $3.0 billion in 2007. AirTran believes that both companies would benefit from this merger by building greater scale, efficiencies and growth opportunities to better succeed in the face of an increasingly competitive airline environment.

Because the network routes of the two carriers are complementary with limited overlap, the combined company would have a national footprint and result in an airline with approximately 1,036 daily departures with 173 unique markets between 74 cities across the United States. The combination of the companies creates a strong growth platform and allows the addition of new cities—more than 30 new non-stop routes and well over 150 additional departures over the next several years.

AirTran Airways expects that the merger will generate more than $60 million in estimated annual synergies, including $40+ million in network synergies and $20+ million in cost synergies. The Company expects the transaction would be accretive to earnings by the end of the first full year following the close of the transaction and significantly accretive thereafter.

Mr. Leonard stated, “As the airline industry becomes more competitive and consolidations are more commonplace, a combination of our two companies ensures the best opportunity for serving our respective constituencies. With our similar cultures, compatible low-cost business models, complementary networks, and fleet commonality, Midwest Airlines and AirTran Airways are as close to a perfect fit as anyone can imagine.

“By joining together, we can deepen our presence in our hubs, expedite the expansion of our network, and strengthen our long-term growth and profitability potential. This will enhance our ability to provide value to travelers, protect the long-term security of our employees and generate significant economic benefits to Milwaukee, Atlanta and all the communities we serve.

“Finally, but certainly not less important, we have the utmost respect for Midwest, its talented employees and the strong loyalty they have built among travelers and the communities they serve. We, at AirTran Airways, have a similar affinity with our constituents, and, in that spirit, we believe that once combined, we can maintain and foster the values and culture that have driven the success of both our airlines. We have full confidence that our commonality will enable us to successfully integrate our two airlines to form a stronger, truly national low-cost airline that will offer Midwest’s constituencies growth opportunities that far exceed what could be achieved independently,” Mr. Leonard concluded.

Below is the letter that AirTran Holdings sent to Midwest’s Board of Directors on December 13, 2006, following the Board’s rejection of the AirTran Holdings proposal:

December 13, 2006

Board of Directors

c/o Mr. Timothy E. Hoeksema

Chairman, CEO and President

Midwest Air Group Inc

6744 South Howell Avenue

Oak Creek, WI 53154

Dear Members of the Board:

As you know from prior conversations and written communications between our companies, we believe that a strategic merger between Midwest Air Group, Inc. and AirTran Holdings, Inc. would serve the best interests of our respective shareholders, customers, employees and communities and better position the combined company to compete against our larger rivals.

We have been trying to privately negotiate a merger between our separate companies for some time. More than a year ago, you declined our initial proposal to acquire Midwest Air Group and you have had our proposal of October 20, 2006 for more than seven weeks. Yet, despite our efforts, and without the benefit of directly discussing with us or our advisors the proposal in detail, our offer was declined on December 7, 2006. Because we believe that the proposal is such a compelling opportunity and offers such significant benefits to your constituents, we feel obligated to make this proposal known and are therefore making public this letter and the supporting financial analysis.

2

Let me recap the benefits our proposal provides. First, we are proposing to acquire all of the outstanding shares of Midwest Common Stock for $11.25 per share in cash and AirTran stock. This offer is a full and generous price based upon publicly available information. It represents a 37% premium to the thirty day average closing price and an 89% premium to the six months average closing price for Midwest’s common stock, prior to October 20, 2006, the date the offer was made to you. Our proposed transaction not only provides Midwest stockholders an immediate premium on their investment, but the opportunity to participate in the future growth of an airline that will possess extraordinary attributes, including an outstanding product for travelers and a highly motivated employee base.

As I said above, despite the fact that we believe that our offer is very attractive from a financial point of view, we would welcome the opportunity to consider non-public information concerning Midwest and are prepared to sit down and enter into serious discussions and, following that, consider in our offer any enhanced values that may be demonstrated. We are also willing to afford representatives of Midwest the opportunity to review non-public information about AirTran Airways and are prepared to enter into an appropriate confidentiality agreement to that end.

Aside from the financial aspects of our offer there are other benefits that a merger of our two companies will provide. Specifically, a combined AirTran Airways and Midwest Airlines: