First NA-26 prototype was flown in 1937. Several modifications of T-6 were built differing only in engines or minor design specifics. G were built. The fuselage is narrow with glazed nose and a small turret in the rear of the fuselage. Wings are unswept with rounded tips.
Tailplane is swept on the leading edge with a rectangular fin centered on either tip.
Landing gear with nose wheel is retractable. The development of B-25 began in 1938. After a series of improvements, NA-62 was demonstrated to USAF and was accepted in the production. First production version was flown on August 19, 1940. The fuselage is narrow with a large radiator under the fuselage aft of the wings.