The Heinkel He 111, one of the best-recognized German bombers of World War II, was developed in the early 1930s by Siegfried and Walter Günter at Heinkel Flugzeugwerke as Germany's secret project ...

The two most famous of the bunch were the Heinkel He 111 and the Junkers 88. ... The twin-engine Ju 88 made its maiden flight on December 21, 1936, and officially became operational in 1939.