"Granted a patent for his turbojet engine in 1936, Ohain joined the Heinkel Company in Rostock, Germany. By 1937 he had built a factory-tested demonstration engine and, by 1939, a fully operational jet aircraft, the He 178. Soon after, Ohain directed the construction of the He S.3B, the first fully operational centrifugal-flow turbojet engine. This engine was installed in the He 178 airplane, which made the world's first jet-powered aircraft flight on August 27, 1939."

https://cs.stanford.edu/people/eroberts/courses/ww2/projects...