PZL P.37 Los

The PZL P.37 Los (Elk) was the most modern aircraft in the inventory of the Polish Air Force in September 1939 and a symbol of Polish technological ingenuity. In fact it was one of the best medium bombers of its time featuring several advanced technological designs, combining good performance and manoeuvrability with high bomb carrying capability. However, too few aircraft were delivered to the front line units by the time WW2 broke out to make a considerable contribution to the Polish war effort in September 1939.

During the Invasion of Poland, from 4 September onward the PZL.37s of the Bomber Brigade were attacking German armoured columns in day attacks, forced by the desperate situation to perform this mission for which they were not designed but, they hampered the advance of the 16th Armoured Corps. They suffered heavy losses due to lack of fighter protection, especially because they usually operated in units of no more than three aircraft at a time. The last combat flights took place on 16 September 1939.

Source:
Info: Wikipedia
http://en.wikipedia.org/wiki/PZL.37_%C5%81o%C5%9B
Profile: Wings Palette
http://wp.scn.ru/en/