P.11g plane was version of P.11c – a development of the inż. Puławski’s P.6 construction under the supervision of inż. Wsiewołod Jakimiuk.
Already in 1937 an upgrade to a more powerful Mercury VIII 840hp engine was considered for the P.11c. This idea was abandoned because calculations shown that the plane will not exceed 400km/h even with the more powerful engine. When the production of Jastrząb (Falcon) fighter equipped with this engine was stopped in April 1939, Airforce command decided to order a new variant of the already outdated fighter. The decision was made to use the supply of 150 already produced engines in newly built P.24 and P.11c figher planes. An order of 90 machines was made for the new version – P.11g, named „Kobuz”. Engine housing was designed fairly quickly by the manufacturer and in mid August 1939 first prototype, built using a serial production P.11c, was flown, then passed the military tests and was accepted for production. Unfortunately the outbreak of war in September made the serial production impossible and the only prototype was evacuated by air to Lwów and from there to Wielicko, near Kowel. There it was armed and drafted into army. It took part in the fighting – on 14th and 15th September Lt. H. Szczęsny won two air fight victories in it. After that the plane was evacuated to Romania and taken into service there.