After the Soviet invasion of Poland in September 1939, the Soviet Union captured several PZL.37 Łoś bombers. These aircraft were subjected to evaluation by the Soviet Air Force’s Research Institute (NII VVS). The exact number of Łoś bombers tested by the Soviet Union is not definitively documented, but at least two aircraft were captured.
The Soviet evaluation of the PZL.37 Łoś commenced on 13 October 1939. By that time, the aircraft had accumulated 97.8 flight hours, completed 519 landings, and its Bristol Pegasus XII engines had been operated for 134 hours. Due to the aircraft’s extensive use, it was considered to be in a state of significant wear, and mechanical issues, particularly with the engine group, were frequently encountered. To enhance crew safety, the take-off weight was reduced to 6,516 kg from the normal 8,570 kg.
The Soviet evaluation of the PZL.37 Łoś concluded in December 1939. Following this assessment, the aircraft was reportedly stored, and probably scrapped soon after.
