The Heinkel He 51 was the first serial fighter of German Luftwaffe. The first prototype named He 51a designed by the Gunter brothers flew for the first time in the summer of 1933. In 1935 has began production of serial He 51A-1 fighters.
The modification He 51B-1 which had provision for a drop tank was produced since 1936. A total of 135 He 51s were shipped to Spain for use by the Legion Condor and the Spanish Nationalists as fighters and fighter-bombers. In He 51 fighters in Spain flew many future aces such as A. Galland, H. Harder, H. Trautloft. The modification He 51B-2 was a seaplane with two floats. They served in I/JG 136 and II/JG 136 of the German Kriegsmarine in late 30s.