Following the developement of the J4, Junkers turned back to his idea of cantilever monoplane fighter aircraft. In early 1917 several designs were developed under the designation J5, of which two became known as J5I and J5II. Both designs were equipped with a remote engine in the rear part of the fuselage. Several engine designs were calculated with a Siemens Sh2 and an Oberursel UR II. None of these designs were built. The J5 represented prestudies of the later J7.

A further study of 1917 is sometimes named under the designator J6, which should have been similar to the J5. However other sources mention the J6 as a Parasol design. Therefore this third cantilever monoplane design might have been a third J5 design. It combines parts of the J5II design with an engine behind the pilot (like the J5I)

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