Vultee BT-13B Valiant The Valiant was the basic trainer most widely used by the U.S. Army Air Forces during World War II. It represented the second of the three stages of pilot training -- primary, basic and advanced. Compared with the primary trainers in use at the time, it was considerably more complex. The BT-13 not only had a more powerful engine, it was also faster and heavier. In addition, it required the student pilot to use two-way radio communications with the ground and to operate land