The PZL P.11 fighter was developed from Zygmunt Puławski’s earlier P.6 design. After Puławski died in 1931, engineer Wsiewołod Jakimiuk continued the project, adapting it to use a more powerful 700-hp engine. Although prototypes were repeatedly modified, they achieved notable successes in international competitions, gaining worldwide attention and generating interest from both Poland and foreign customers.
In 1933 the P.11a, powered by a Bristol Mercury IV engine, was created for the Polish Air Force. It passed tests that spring, leading to an order of 30 aircraft, later expanded to 50, though production was delayed by Romanian orders for the P.11b. Manufacturing began in spring 1934 and finished by summer.
The P.11a remained in frontline Polish service during the 1939 Defense War, fighting from the first day until the evacuation after the Soviet invasion on 17 September. Surviving aircraft were interned in Romania for training use, and one later served in Hungary as a glider tug.