North American BT - 9 The North American BT - 9 was a low - wing single piston engine monoplane primary trainer aircraft that served with the United States Army Air Corps ( USAAC ) and other allied countries during World War II . It was a contemporary of the Kaydet biplane trainer and was used by pilots in Basic Flying Training following their completion of Primary in the Kaydet . In United States Navy ( USN ) service it was designated the NJ - 1 . Design and development . The BT - 9 , designated NA - 19 by the manufacturer , evolved from the North American NA - 16 , which first flew in April 1935 . The BT - 9 design first took to the skies in April 1936 . Fabric covered the movable surfaces on the tail and wings , as well as the sides of the fuselage from just behind the firewall to the tail . The remainder of the aircraft was metal - covered and featured fixed ( non - retractable ) landing gear . The Army Air Corps purchased a total of 199 BT - 9s , BT - 9As and BT - 9Bs . Many foreign countries also used variants of this aircraft under North American ' s NA - 16 designation . The BT - 14 ( NA - 58 ) and the similar NA - 64 Yale represented a major aerodynamic improvement over the NA - 16 series , with a longer all metal fuselage replacing the fabric covered fuselage of the earlier NA - 16s . The BT - 14 featured a Pratt & Whitney R - 985 engine versus the Wright R - 975 used on the BT - 9 and NA - 64 . As well as metal skin replacing the fabric on the fuselage , the fin was changed from having a corrugated surface on the BT - 9s to being a smooth stressed skin structure and was moved aft slightly , lengthening the rear fuselage while the engine was moved forward to maintain the CG . The rudder was also changed from the rounded shape used previously to one with a roughly triangle shape with the broadest part being at the bottom , and the canopy was redesigned . The new fuselage would provide the basis for the entire AT - 6 family , when fitted with the larger Pratt & Whitney R - 1340 engine , a new wing with retractable undercarriage and minor changes for a gunners position . The BT - 9 and NA - 64 suffered from stall / spin problems and a variety of fixes were tried . The USAAC temporarily settled on using slats on the later versions of the BT - 9 however these did not work well , and later developments would have the outer wing panels swept forward slightly so that they no longer had the straight trailing edges of the BT - 9 and NA - 64 . The later swept forward wings were fitted to the BT - 14 . Operational history . The NA - 64 retained the fixed undercarriage layout and was built for the French Armée de l ' Air and Aéronavale in 1939 – 1940 . Just under half were delivered before France surrendered to the Nazis and the remaining aircraft were purchased by the British Purchasing Commission for the Royal Canadian Air Force ( RCAF ) . The RCAF named the type the Yale , and were used initially as intermediate pilot trainers and later as airborne wireless radio trainers . All were sold as scrap post - war but approximately 40 survive today , with about 15 in airworthy condition . The NA - 26 , an improved model with retractable landing gear which became the prototype for AT - 6 Texan advanced trainer , was developed from the NA - 16 design . The Australian CAC Wirraway was also developed from the NA - 16 . Survivors / Aircraft on display . There are many surviving NA - 64 Yales today because of Ernie Simmons , a farmer from near Tillsonburg , Ontario . Simmons bought over 30 Yales in 1946 and kept them on his farm until he died in 1970 . These aircraft were subsequently auctioned in 1970 , and have been restored by museums and warbird enthusiasts . Most of the Yales currently in existence came from the Simmons collection .