Midwest Airlines ( MEH) pushed back Thursday against a hostile takeover bid by AirTran ( AAI), characterizing the offer as "opportunistic" and undervaluing the company.

AirTran has offered $345 million in cash and stock for the Milwaukee-based carrier and has called on stockholders to tender their shares by Feb. 8.

In an SEC filing, Midwest said its board has determined that the offer doesn't adequately reflect its growth prospects.

"The board believes that Midwest and its shareholders are poised to realized the benefits of Midwest's long-term strategic plan, and that today's earnings announcement indicates that those efforts are driving growth for the company," said CEO Timothy Hoeksema in a prepared statement.

Midwest reported that fourth-quarter net income was $3.6 million, or 16 cents a share. Revenue rose 18% from a year ago to $168.3 million. Three analysts surveyed by Thomson Financial forecast earnings of 11 cents a share.

"Our performance was very strong, resulting in our third consecutive quarterly profit and continuing the turnaround for Midwest Air Group," Hoeksema said. A year earlier, the airline lost $13.8 million in the fourth quarter.

For the full year, Midwest reported net income of $5.4 million, compared with a $64.9 million loss in 2005.

AirTran said it was sorry to learn of Midwest's decision. "We believe that the Midwest board and management have been negligent in meeting their fiduciary obligations and we urge the company's owners to tender their shares to let the board and management of Midwest know that they want Midwest to explore the merits of the merger," said AirTran CEO Joe Leonard in a prepared statement.

AirTran values its offer at $13.25 per Midwest share. The shares were recently trading at $13.02, up 43 cents, or 3.4%.

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