a prototype ss.4 was built at the "società aeronautica italiana - ambrosini" factory in passignano sul trasimeno, umbria. the first flight took place in 1939, and extensive testing took place at guidonia over the course of 1940 and 1941, until a landing accident destroyed the prototype and killed the test pilot. a second prototype was ordered immediately, but development priority was placed on more easily developed wooden aircraft, and the ss.4 design was abandoned in 1942.