In World War II the North American T-6 Texan / Harvard was the most important trainer of the allied air forces, and around 17,000 were built. The first of the series was the NA-16 prototype which flew for the first time in April 1935 as a completely metal monoplane with a low placed wing, two open cockpits a fixed undercarriage and a 298 kW Wright R-975 engine.

Mounted with a glass hood, the type was ordered as the BT-9 and the NJ series for both the US Army and US Navy. Other planes were produced for export to numerous countries like Canada where the plane was known as the "Yale". This NA-18 version was further developed with a 447 kW Pratt & Whitney R-1340 engine, cockpit modified as a common fighter cockpit of those days and a retractable undercarriage and tail wheel. This version was specially for the combat training of the new pilots, and was ordered for the first time as AT-6 Texan (normally BC-1) and as the SNJ series for the US Army and Navy.

Production was started in numerous improved and more specialized types up to the T-6F and SNJ-6.

In the USAAF the AT-6C and AT-6D were the most used (2.970 6C's were build, and 4.388 6D's ! ) in the Navy 2.400 SNJ-4's and 1.357 SNJ-5's were used. Also the British and their allies within the common wealth used the type in large numbers with basic mark "Harvard" that were delivered from American and Canadian (Noorduyn) production in types up to the Harvard Mk 4.