In 1937, North American Aviation, Inc began work on an attack version of its BC-1A advanced trainer, which was later to be redesignated AT-6. The attack version was intended primarily for the export market.
A demonstration model, the NA-44, was first flown in 1938. It was powered by a 775-hp Wright R-1820-F52 air-cooled radial engine and was armed with five guns. This aircraft was eventually sold to Canada in 1940.
Brazil received thirty examples under the designation NA-72 from July to October of 1940.
Ten more were ordered by Thailand on November 29, 1939 as NA-69s. They were completed by September of 1940 and were about to be shipped to Thailand. However, fearful that they might fall into Japanese hands, they were intercepted by American authorities and impressed into service under the designation A-27 and assigned the serials 41-18890/18899. They were sent to serve in the Philippines, where they were attached to the 24th Pursuit Group. They were there when the Japanese struck in December of 1941. It is believed that most were quickly destroyed in the initial Japanese onslaught, although some of them may have survived as squadron hacks until at least the beginning of March 1942.
One Wright R-1820-75 air-cooled radial engine rated at 785 hp for takeoff and 745 hp at 9600 feet. Performance: Maximum speed 250 mph at 11,500 feet. Cruising speed 220 mph . Landing speed 70 mph. Service ceiling 28,000 feet. Range 575 miles with 400 pounds of bombs. 800 miles maximum range. Dimensions: Wingspan 42 feet 0 inches. Length 29 feet 0 inches, height 12 feet 2 inches, wing area 258 square feet. Weights: 4520 pounds empty, 6000 pounds gross, 6700 pounds maximum. Armament: Two fixed forward-firing 0.30-inch machine guns in the nose, one flexible 0.30-inch machine gun in the rear cockpit. A load of four 100-pound bombs could be carried underneath the wings.