Junkers setbacks with crashes of prototypes in 1937 and 1938. Further refinements enabled certification in 1939 and spurred South African Airways to make an initial order for two aircraft fitted with US-built Pratt & Whitney engines. Just as the aircraft was being readied for its first commercial flights, World War II began. With the outbreak of hostilities, all models were requisitioned by the Luftwaffe for military air-transport roles, and later, long-range maritime patrol. Military aircraft production was begun by the company in the 1930s and eventually monopolized all its resources. Perhaps the most notable design was the Junkers Ju 87 "Stuka"
Hugo Junkers communist activist, as Managing Director of what remained of his business. Hugo Junkers is mainly known in connection with aircraft bearing his name. These include some he reluctantly developed for the German Empire during World War I, later in minor association with Anthony Fokker, as well as civil aircraft designs during the "interwar period" produced by "Junkers Flugzeugwerke" (Junkers Aircraft Works). Junkers died in 1935. The earliest all-metal post-World War I aircraft designs of both Andrei Tupolev — with his Tupolev ANT-2 two-passenger small aircraft of 1924 — and William Bushnell Stout's initial all-metal design, the Stout ST twin-engine torpedo