The S.55 featured many innovative design features. All the passengers or cargo were placed in the twin hulls, but the pilot and crew captained the plane from a cockpit in the thicker section of the wing, between the two hulls. The S.55 had two inline counter-rotating propellers, mounted in tandem. The engines were canted sharply at an upward angle. Two wire-braced booms connected the triple-finned tail structure to the twin hulls and wing.
Even though its design was unusual, the Savoia-Marchetti S.55 was a remarkably airworthy craft. In 1926, the S.55P prototype set 14 world records for speed, altitude and distance with a payload. The S.55's greatest successes, however, were its many flights between Europe and the Americas.
The first staged south Atlantic Ocean crossing was made in 1922 using three different Fairey III machines and the Dornier Do J Plus Ultra crossed in January 1926 with a single stop at the Cape Verde Islands.
The first S.55 crossing was made a year later by the Santa Maria under Francesco de Pinedo. After flying south to Bolama, at that time in Portuguese Guinea they hoped to cross the ocean without another stop but were forced down at Cape Verde, reaching Brazil on 23 February 1927. After the crossing, the aircraft was traded to Brazil for coffee beans.
The Brazilian João Ribeiro de Barros and his crew of three made another crossing in S.55 "Jahú" on 24 April 1927. Departing from Santiago Island, he crossed the Atlantic in "Jahú" and landed at Fernando de Noronha Island, Brazil.
Pilots Francesco de Pinedo and Carlo del Prete took off from Sesto Calende, Italy, in an S-55.[when?] Four months later, they arrived back in Italy, having flown nearly 48,280 km (30,000 mi) in 193 flying hours and having made just over 50 stops, including Rio de Janeiro, Buenos Aires and New York City.
On 20 June 1928 Savoia-Marchetti S.55 I-SAAT Santa Maria, piloted by Ten. Col. Umberto Maddalena of the Italian air force, located survivors of Arctic explorer Umberto Nobile's crashed airship Italia on an ice floe about 120 km (75 mi) northeast of Nordaustlandet, Svalbard.