At first, he returned to Rheydt to work in his father's company, but soon attended further lectures on electromagnetism and thermodynamics held by Adolf Slaby in Charlottenburg.

Junkers personally introduced the calorimeter at the 1893 World's Columbian Exposition in Chicago, where it was awarded a gold medal.

Reissner had developed an all-metal aircraft, on which work first started in 1909 at the Brand Heath, equipped with corrugated iron wings built by Junkers & Co. in Dessau.

In 1915, he developed the world's first practical all-metal aircraft design, the Junkers J 1 "Blechesel"[1] (Sheetmetal Donkey), which survived on display at the Deutsches Museum in Munich until WWII.

During this time, the German government's IdFlieg military aviation inspectorate forced him to merge his firm with Anthony Fokker's to form the Junkers-Fokker Aktiengesellschaft on 20 October 1917.

[2] The J.I's pattern of an armored fuselage that protected the nose-mounted engine, pilot, and observer in a unitized metal "bathtub" was the possible inspiration[citation needed] for Sergey Ilyushin's later Il-2 Shturmovik (conceivably appropriate as Junkers did have a manufacturing plant in Fili, a suburb of Moscow, in the Soviet Union in the 1920s) with a similar armored fuselage design.

Airlines where Junkers played a pivotal role in early phases of their development include Deutsche Luft Hansa and Lloyd Aéreo Boliviano.

Several business ventures failed from wider economic or political problems that hampered sound engineering plans.

Junkers always had more ideas: the massive four-engined G.38, nicknamed "Der Grosse Dessauer", delivered to Luft Hansa, made no commercial trips for many months as he repeatedly recalled it to the factory for improvements.

They responded by demanding ownership of all patents and market shares from his remaining companies, under threat of imprisonment on the charge of high treason.