National Air Transport (NAT), Boeing Air Transport (BAT), and Stout Air Services were three early airmail carriers. NAT was formed in 1925 by Clement Keys, and in 1927 won the bid for the New York to Chicago Airmail route. BAT received the Chicago to San Francisco route in 1927, and also carried passengers. Stout Air Service was formed in 1925 and carried mail and passengers from Detroit to Cleveland. These three companies were all predecessors of United Air Lines, which was formed in 1929.