The S.A.I.403 was an exceptional fighter in several respects, and the prototype, completed in late 1942, possessed excellent handling characteristics and a performance higher than those of most contemporary fighters with twice the power. The structure was sturdy and facilitated mass production, and the use of wood made possible far greater dispersal of production, simplified repairs and conserved stocks of strategic materials.
In January 1943 an order was placed by the Italian Air Ministry for 3,000 S.A.I.403 fighters. This order supplanted that previously placed for 2,000 S.A.I.207 fighters, and 1,200 were to be produced by Savoia-Marchetti, 1,000 by Caproni, and the remainder by Ambrosini. Tooling had reached only the initial stages, however, when the armistice terminated all further work on this outstanding fighter.
Span: 32 ft 1.75 in (9.80 m)
Length: 26 ft 10.75 in (8.20 m)
Height: 9 ft 6 in (2.90 m)
Wing area: 155.65 sq.ft (14.46 sq.m)
Weight empty: 4,372 lb (1,983 kg)
Loaded weight: 5,820 lb (2,640 kg)
Max speed: 403 mph (648 kmh) at 23,620 ft (7,200 m)
Climb: to 19,685 ft (6,000 m) 6.66 min
Range: 582 mls (937 km)