Junkers J 21

The Junkers J 21 was a German low‑wing monoplane developed in the early 1920s as part of Junkers’ pioneering all‑metal aircraft program. Designed by Hugo Junkers, the J 21 first flew in 1924 and served primarily as a reconnaissance and army‑cooperation aircraft for the Reichswehr. Its all‑duralumin construction, corrugated skin, and cantilever wing eliminated the need for external bracing, showcasing the durability and aerodynamic efficiency that would become hallmarks of Junkers designs. Powered by a 260‑horsepower BMW IIIa inline engine, the aircraft could reach a maximum speed of 170 km/h (105 mph) and a service ceiling of 5,000 meters, offering reliable performance in the harsh post‑war environment. The crew of two operated a single, forward‑facing cockpit with a flexible rear gun position, while the generous payload allowed for cameras, radios, and light bomb loads. Though only a small production run was completed before newer models such as the Junker Ju 52 superseded it, the J 21 demonstrated the viability of metal monoplanes and influenced subsequent military and civilian aircraft. Its legacy lies in confirming Junkers’ construction philosophy, which reshaped aviation standards worldwide. Today, the few surviving examples are displayed in museums, reminding enthusiasts of an era when metal aircraft began to dominate the skies.