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)
Type J5I Single seat fighter J5II Single seat fighter J5III Single seat fighter
Engine 1 Siemens Sh 2 1 Siemens Sh 2 1 Benz DIIIa
Dimensions Length 8,00 m, span 11,80 m, wing area 20,00 m2 Length 6,75 m, span 8,60 m, wing area 12,00 m2
Weights Empty 465 kg, flying weight 660 kg Empty 355 kg
Performance Max.. speed  , cruising speed  , range , endurance  , service ceiling   , climb
Armament