Built in 1936 as a heavy bomber, the Z.508 flying boat was a three-engined, much enlarged development of the Z.501. Fitted with 840 h.p. Isotta-Fraschini Asso XI R.C.40 engines, the Z.508, like nearly all Zappata-designed aircraft, set a number of international records. In 1937 Mario Stoppani flew the Z.508 to an altitude of 6560 ft. with a load of 22,000 lb., and at speeds of 154.26 m.p.h. and 156.42 m.p.h. carrying 11,000 lb. over respective 1242-mile and 621-mile courses. The Z.508 was unsuitable for the intended bombing role and was never employed militarily.
Specifications included a span of 98 ft. 5 in., a length of 70 ft. 5 in., and a height of 18 ft. 7 in. Maximum speed was 196 m.p.h. and alighting speed 75 m.p.h.