A HA-11/33 was purchased by the Austrian Air Force, and was subsequently absorbed into the German Luftwaffe following the Anschluss. Deemed worthy of further development, WNF (which had absorbed Hirtenberg, which itself had taken over Hopfner) was tasked with developing it into a military training aircraft for flying boat pilots. Designated WNF Wn 11 by the RLM, testing was undertaken at Travemünde in 1940, but the type was not ordered into production.