During the war years the C.R.D.A. completed two prototypes of the Z.511 commercial transport floatplane designed by Zappata before the war and intended far use on Alitalia's South Atlantic route as the world's largest floatplane. Construction of the Z.511 commenced in 1941 and the first prototype flew on 8th September 1943. The first prototype was destroyed when it struck a mine, and the second, commandeered by the Luftwaffe, was destroyed in Germany. The Z.511 was powered by four 1,500-h.p. Piaggio P.XII R.C.35 radials and had a loaded weight of 74,957 lb.