Northwest is a minority partner in the deal for the small airline.

Rick Schifter, a TPG partner, said Friday a merger agreement was reached late Thursday, the Wall Street Journal reported. He said in a conference call that TPG sees several ways to cash out of Midwest, including a sale to Northwest or to the public.

He said however that may be years away.

Midwest's board unanimously agreed to a sweetened, $17 a share, all-cash offer from TPG and Northwest, spurning a cash-and-stock bid valued at $16.27 a share from AirTran.