By January 1940, over half of the original production batch had been completed. Beyond the initial production order in April 1937, follow-on orders had been issued for the type; in February 1938, an additional 202 Defiant Mk I aircraft were ordered; three months later, another 161 aircraft were ordered. In December 1939, yet another 150 aircraft were ordered, raising the overall total to 513. In 1940, this rose to 563 Defiant Mk Is on order, while a further 280 were ordered under a rearranged manufacturing plan issued in mid-1940. However, the performance of the Defiant had been determined to be inadequate by this point, which led to manufacturing being sustained principally for economic reasons. A total of 713 Defiant Mk I aircraft were completed.