The SIAI-Marchetti SIAI S.9 is an aircraft designation that appears in certain aviation databases, such as those utilizing ICAO type codes, but it lacks any corroborating evidence in historical aviation records. Despite the designation and its classification as a seaplane, there is no documentation in manufacturer histories, museum collections, or primary aviation sources to suggest that an S.9 was ever designed, tested, or produced. It is highly probable that the S.9 entry is a database artifact or a mislabeled coding entry rather than a physical aircraft.
To understand the context of this designation, one must look at the history of the manufacturer. The company was established in 1915 as Società Idrovolanti Alta Italia (SIAI) in Sesto Calende, Italy, located on Lake Maggiore. From its inception, SIAI specialized in the development of seaplanes for the Italian armed forces. The company's trajectory was significantly influenced by chief designer Alessandro Marchetti, leading to the adoption of the Savoia-Marchetti name. During the interwar period and World War II, the firm produced several highly successful and well-documented aircraft, including the S.16, the S.55 flying boat, and the SM.79 Sparviero bomber.
Throughout the mid-20th century, the company underwent several corporate transitions. It was formally renamed SIAI-Marchetti in 1943. By 1983, the company ceased to exist as an independent entity after being absorbed by Agusta. Further consolidation occurred in 1997 when its designs and activities were integrated into Aermacchi. Today, this lineage is maintained under Leonardo S.p.A., the modern Italian aerospace group, which continues to market the SF-260 family—a descendant of the SIAI-Marchetti design lineage. While the manufacturer produced a vast array of maritime and land-based aircraft, the S.9 remains absent from all verified type lists, contrasting with the extensive documentation available for other SIAI and Savoia-Marchetti models.