S9
S9 may refer to: == Transportation == SIAI S.9, a 1918 Italian flying boat Aircraft registration prefix of São Tomé and Príncipe USS S-9 (SS-114), a 1920 S-class submarine of the United States Navy County Route S9 (California) Rans S-9 Chaos, a light aerobatic aircraft East African Safari Air's IATA code === Rail === S9 (Berlin), an S-Bahn line in Germany S9 (Milan suburban railway service) in Italy S9 (RER Vaud), an S-Bahn line in Switzerland S9 (Rhine-Ruhr S-Bahn) line in Germany S9 (Rhine-Main S-Bahn) line in Germany S9 (St. Gallen S-Bahn), a line in the canton of St.