The PZL P.11 was a Polish fighter aircraft, designed in the early 1930s by PZL in Warsaw. It was briefly considered to be the most advanced fighter aircraft design in the world. The PZL P.11 served as Poland's primary fighter defence in the Polish campaign of 1939, but by that point was outdated due to rapid advances in aircraft design.
The gull-winged PZL fighter formed the back bone of the Polish Air Force when the Soviet Union declared war on them in the final days of 1938. Soviet pilot Sergei Yaroslavsky found that the fighter wasn't nearly as dangerous as the 109, but it was still capable of being a threat to the SB-2.