In late 1916, the demand for a durable observation aircraft capable of performing ground attack missions led to the introduction of the Junkers J.I. Developed in early 1917, it was the world’s first all-metal aircraft produced in quantity. Eliminating the need for external bracing wires, the fuselage, wings and tail were constructed of Duralumin while the engine and two-man crew were protected by a nose-capsule of 5-mm chrome-nickel sheet-steel. Although this unique design resulted in a strong and durable aircraft capable of surviving the effects of enemy ground fire, the Junkers J.I was heavy, cumbersome and took forever to get off the ground.
REPORT ON THE JUNKER ALL-METAL ARMOURED BIPLANE TYPE J.I., July 1919 Reports on German Aircraft 14
A valuable report on two machines, one that was saled by British troops near La Vacquerie during the German retreat 1918, and one brought down by the French using armour piercing bullets fired from the ground. The report notes that the Junker is radically different from the usual type of aeroplane.