sentences:  The second aircraft (BuNo.75726), with a larger stabilizer, was evaluated by the USAF in 1949 as a replacement for the AT-6, with the USAF selecting it on 24 March 1949 as a primary trainer.Designed to be aerobatic to teach pilots maneuvers, such as stalls, spins and rolls, Fairchild received a contract for 100 model 129s under the USAF designation T-31.