numbers, P.11s downed a considerable number of German aircraft, including fighters. The exact numbers are not verified, but some sources claim that at least one German aircraft was shot down for each P.11 lost (a figure of 107 to 141 German aircraft shot down for the loss of 118 Polish aircraft is most often given). One of the most interesting units in the Polish Air Force arsenal was the PZL.37 Łoś twin-engine medium bomber. Before the war it was one of the world's most modern and outstanding bombers. Smaller than most contemporary medium bombers, it was still able to carry a heavier bomb load than comparable aircraft, including the famous Vickers Wellington. It was relatively fast and easy to handle, and thanks to a landing gear with double wheels, it could operate from rough fields or meadows. The only drawback was its relatively weak defensive armament, consisting of 3 machine guns. Its range was also limited, but the Łoś was not meant to be a long-range bomber. During the September Campaign, despite their good performance, they were too few in number to change the outcome and, often lacking fighter cover, sustained heavy losses, especially when used to attack armoured columns. Few Polish Air Force planes were destroyed on the ground as most had been deployed to temporary, secret airstrips. The fighter planes were grouped in 15 escadres. Five of them constituted the Pursuit Brigade (Brygada Pościgowa), deployed in the Warsaw area. The bombers, grouped in 9 escadres of the Bomber Brigade (Brygada Bombowa), attacked armoured columns, suffering heavy losses. Seven reconnaissance and 12 observation escadres, attached to various Polish Armies, were intensively used for reconnaissance. However, the Polish pilots, while highly trained and motivated, faced a numerically superior opponent in superior designs with a much better command structure. Germany achieved air superiority around day three of the campaign, although the Polish Air Force managed to remain operational for the first two weeks of the September Campaign. At that point, the Polish Air Force ceased to exist as a fighting force, as most of its planes were either destroyed in combat or, facing rapidly advancing German troops, had to be abandoned on the ground due to lack of supplies and spare parts. A few remaining aircraft were either captured by the Germans or withdrawn to Romania and taken over by that country. A great number of pilots and air crews managed