I. "Gruppe" was formed at Langendiebach on 1 May 1939. This unit was formed from I./KG 155. The unit was expanded and trained on the He 111 through to 26 August. The "Gruppe" was placed on alert on that day and transferred to Dedelstorf on 31 August 1939 under the command of "Gruppenkommandeur" (Group Commander) "Major" Walter Traub. The group remained active until 1 May 1943 when it was re-designated "Lehrgeschwader" 1 (Training and Experimental Wing 1) and transferred to that wing. I./KG 55 was reformed on 10 June 1943 at Stalino in the Soviet Union using personnel from "Transportfliegergruppe" 10, the former "Kampfgruppe zur besonderen Verwendung" 5 (KGr. z.b.v. 5, Fighting Group for Special Use).