Upon the flight of the prototype with only a single stablilized tail, it felt more like a fighter than a bomber, high speeds and quick turns, the only thing missing was a stable plane and earned the nickname "the flying pencil". Adding a second tail allowed this bomber to be one of the most maneuverable through the beginning of WWII. After seeing combat in the Spanish Civil War several updates to the Dornier were made and the 17z became the most common variant with an extended cockpit and canopy adding more room in the fuselage for another gunner in the rear position. With the updates the bomb loads were impacted as well as speed and altitude. Although it started the beginning of the war as one of the most promising aircrafts, but by 1940 it was becoming obsolete as production of more powerful aircrafts started to be released and started overtaking what previously was considered the best medium bombers.