The first prototype of the Macchi seaplane was a single-seat sesquiplane fighter which first flew in 1917. Developed by engineers Buzio and Calzavera it had a single-step hull and an open cockpit forward of the wings and was similar to the earlier Macchi M.3. It was followed by another prototype with a revised tail unit designated the Ma and further developed as the M bis and Ma bis. The production aircraft was designated the M.5 and like the prototypes was powered by a single Isotta Fraschini V.4B engine in pusher configuration. Deliveries soon commenced in the summer of 1917 to the Aviazione per la Regia Marina (Italian Navy Aviation). Late production aircraft had a more powerful Isotta Fraschini V.6 engine and redesigned wingtip floats, they were designated M.5 mod. Macchi produced 200 aircraft during WW1 and another 44 were built by Società Aeronautica Italiana. The M.5 was operated by five Italian maritime patrol squadrons as a fighter and convoy escort.