PZL 37 “LOS” (Moose) was the most modern aircraft as part of the Polish Air Force during the German invasion in September 1939. The aircraft was designed in 1934 by Jerzy Dabrowski. The publication includes the origins and development of construction of bombers in Poland. A detailed technical description of all the PZL 37 versions. The author also presents the course of fights with the use of PZL 37 in September 1939. The book contains numerous photographs, drawings of aircraft projects, and the colorful boards with camouflage and markings.