The Department of Justice has announced it will not challenge American Airlines’ proposed buyout of St. Louis-based Trans World Airlines. Justice Department approval was considered to be the final major hurdle in the $4.2-billion plan. There are still court appeals from those who lost out in the T.W.A. speepstakes, and approval from the airline’s unions is needed. But officials at T.W.A. now expect the deal with American will go through and they’re hoping for a quick transation process. An American Airlines official says the deal should be completed by early next month.