Works on P.37 project were started in 1934 on the command of inz.(engineer) J.Dabrowski. First prototype P.37/I was build in 1936. P.37/I had Bristol "Pegasus" XIIB [642 kW (873 KM)] engines. First flights piloted by J.Widawski showed that construction of P.37 had to be modified. Tests on P.37/I were finished in 1937. Second prototype P.37/II had modified fuselage, wings, tail and two-wheel undercarriage. P.37/II had better engine Bristol "Pegasus" XX [675 kW (918 KM)] .Decided that it is pre-production variant of P.37A, which was produced. But first 10 Loses (of first 30) had "Pegazus" XIIB engines, rest had "Pegazus"XX. One of preserie Loses marked by civilian number SP-BNL was showed in 1938 for Romanian, Greek Bulgarian and Yugoslavian air forces. SP-BNL was also showed on International Air Show at Belgrade. Modified SP-BNL was prototype of P.37B. Polish Air Force ordered 100 P.37B with "Pegazus"XX engines produced in Poland as PZL Bristol "Pegaz"XX. Last works on P.37B were finished at summer 1939. Later PZL Industries worked on next version P.37/III. (used modified P.37A) This P.37 had engines Gnome-Rhone 14NO and 14 NO1, was marked as PZL P.37C.It was export version. In 03.1938 P.37/III (P.37C) was showed in Turkey and Greece. Later Bulgaria ordered 15 Loses, Yugoslavia 20 Romania 30 and unknown number Iran. P.37C was offered also for Turkey, Finland, Estonia and Greece. P.37C was not delivered to foreign countries because of start of WWII on 1.09.1939.

PZL P.37 was one of the most modern aircraft of WWII. Had many modern technologies. For example: spot welding construction (big part) and laminar airfoil ( discovered during works on P.37).

P.37 IN POLISH CAMPAIN:

History of sorties made by P.37 in 1939 is so long. I will describe it in short version: Polish Air force had in 1.09.1939 36 P.37 in battle service and a few tens in reserve. P.37 did at least 135 sorties. Dropped 120 tons of bombs. P.37 used mainly 110kg Z-31"Myszka" ("Mouse") bombs. P.37 destroyed many Germans equipment. Once German loses because of P.37 Los bombings were as large as Germans decided to attack Warsaw a few days later! P.37 shoot down at least 3 Me-109 and one He-111. Combats showed that armor and defensive armament of P.37 is to small. Poles lost 27 P.37s (75%).

- 11 were shoot down by German fighters (1 on the ground)
- 5 was shoot down by anti aircraft artillery (1 destroyed and 4 crashed during landing because of damage)
- 2 were destroyed during bombing.
- 1 was shot down by Polish artillery (!)