 Testing was then unexpectedly halted as the testing officer, Lützow-Holm, was ordered to Svalbard to take part in the search for the missing polar explorer Roald Amundsen and his two Dornier Wal flying boats.The prototype, F.120, was used as a target aircraft during anti-aircraft artillery demonstrations on 13 September 1925, fitted with skis in February–March 1926 and was handed over for active service on 15 July 1926.F.120 exceeded all expectations as to speed, rate of climb and maximum altitude, leading the way for the manufacture of the remaining three aircraft on order from July 1925.