The United States armed forces standardized on three types – a Primary trainer, of which the Stearman PT-13/PT-17 is the best known, a Basic trainer such as the Vultee BT-13, and an advanced trainer such as the well known North American AT-6 Texan, which would also be widely exported to the Commonwealth countries as the Harvard. In addition, production of various combat types was diverted to training although considerable effort was made to cover all possible types of training with purpose built types.