SIAI entered the S.50 in the 1923 Regia Aeronautica (Italian Royal Air Force) fighter contest, even though the S.50 was powered by a 212-kilowatt (285-horsepower) SPA 62a six-cylinder engine instead of the 224-kilowatt (300-horsepower) Hispano-Suiza HS 42 eight-cylinder water-cooled engine required by the Italian Air Ministry's specification for entrance in the contest.

Despite this, the S.50 attracted enough Regia Aeronautica interest to prompt it to acquire three S.50 fighters from SIAI for evaluation, although a proposal to order twelve S.50 aircraft never bore fruit.

[1] Marchetti decided to design a derivative of the S.50 powered by the HS 42 engine for entry in the 1923 fighter contest.

The resulting S.52 was a single-seat, all-metal biplane with its fuselage suspended between the upper and lower wings.

[6] Data from Green, William, and Gordon Swanborough The Complete Book of Fighters: An Illustrated Encyclopedia of Every Fighter Aircraft Built and Flown, New York: SMITHMARK Publishers, 1994, ISBN 0-8317-3939-8General characteristics Performance Armament Notes: Related development