Hugo Junkers was was professor of mechanical engineering at Aachen before becomming involved in the production of aircraft during the First World War. In 1918 he designed the world's first all-metal plane, the Junkers D-I. Construction difficulties resulted in only 41 aircraft reaching the front-line.

Junkers also designed the CL-I, considered by many to be the best German ground attack plane of the war. However, only a few Junkers CL-I got to the Western Front before the signing of the Armistice in November 1918.