The SAI.403 Dardo was a more sophisticated version of the SAI.207 with the same type of stressed-skin wooden construction, but which had fully retractable landing gear rather than the 207's combination of retractable main gear and fixed tailwheel. In addition, changes included a revised tail unit with a variable-incidence tailplane, greater ammunition capacities, and an upgraded powerplant in the form of the 750 hp Isotta-Fraschini Delta RC.21/60 Serie I-IV driving a three-bladed Piaggio constant-speed propeller.