The twin-hulled flying boats built by Savoia-Marchetti in the 1920s/1930s helped Italy achieve prestige on the world stage of aviation.
Originally designed as an amphibious bomber and maritime patrol craft, the S.55 would go on to become a popular civil transport. Together it and the larger S.66 would fly numerous commercial routes around the Mediterranean.
The S.66 was developed as an enlarged version of the S.55 with the aim of replacing the S.55P. The S.66 was a twin-hull cantilever monoplane flying boat with metal hull and wings and wooden twin-booms and tail unit.
The two crew had enclosed cockpit mounted in the wing centre section between the two hulls, each hull contained seven seats, two sleeping couches and a lavatory.
The prototype first flew in 1931 powered by three Fiat A.22 R. engines strut-mounted above the wing. The company built 23 production aircraft with three 559 kW (750 hp) Fiat A.24R engines and the sleeping couches were replaced by two to four more seats in each hull.
Sources: YouTube; Wikipedia