Midwest Airlines parent Midwest Air Group entered a "definitive merger agreement" with TPG Capital

, after AirTran Airways parent AirTran Holdings this week had sweetened its offer for the Milwaukee-based airline. Expected to close by year-end, the TPG transaction is valued at $450 million and includes financing from Midwest codeshare partner Northwest Airlines. TPG said an "expanded alliance" with Northwest would "lead to a bigger and better Midwest." AirTran CEO Joe Leonard said his carrier "doesn't need to merge with any other carrier to achieve our business goals."