KANSAS CITY, Mo. — Northwest Airlines would be a minority investor in the buyout of Midwest Airlines, but a very sizable one.

Northwest would own 47 percent of the Milwaukee-based carrier under Midwest Air Group Inc.'s agreement to be acquired by a Texas private equity firm.

The size of Northwest's stake was among the details released in the proxy statement filed last week by Midwest delineating its deal to be bought by TPG Capital for $17 a share.

Northwest would provide $213.3 million of the $451.4 million price tag that Midwest's board approved last month. The deal thwarted an eight-month public effort by AirTran Holdings Inc. to acquire Midwest and create a national discount carrier.

AirTran declined to comment on the disclosure regarding Northwest's stake.

TPG and Midwest executives have said Northwest would be a passive investor. The airline would not have a representative on the new Midwest board, nor any management role in running Midwest.

"That's what is meant by 'passive investor,' " said Carol Skornicka, Midwest's senior vice president and general counsel. "We intend to compete vigorously with Northwest in the markets we both serve."

However, many airline analysts note that Northwest, which is based in Minneapolis, joined the TPG bid to keep AirTran from establishing significant operations in the upper Midwest.

"I've followed Northwest Airlines for 38 years, and the word 'passive' is never one that comes to mind," said Terry Trippler, travel expert for www.terrytrippler.com. "What looked like a very good defensive move for Northwest may ultimately turn out to be a very good offensive move. It may be sooner rather than later that Northwest will have at least a 51 percent stake in Midwest."