Appearing in 1937, the P.50-I four-engined heavy bomber employed a number of features tried on earlier Piaggio and Reggiane experimental models, among them the tandem engine layout of the P.23M and the basic fuselage of the Reggiane-built P.32bis, but it was a much larger machine. The four engines were 730 h.p. Isotta-Fraschini Asso XI R.C. twelve-cylinder vee units driving two tractor and two pusher three-bladed airscrews. The wing (mounted in shoulder position), the fuselage, and the tail surfaces were of welded steel construction, fabric-covered, while the movable control surfaces were wood. The tail was the normal single fin-and-rudder type similar to that of the P.108, of which the P.50-I and P.50-II were essentially prototypes. The P.50-II (1938) employed four 1000 h.p. Piaggio P.XI R.C.40 fourteen-cylinder radial engines mounted in normal fashion, this being the arrangement adopted for the P.108 (with, however, the higher-powered P.XII R.C.35 units).
Dimensions of both versions of the P.50 were: span 84 ft. 7 1/2 in., length 64 ft. 11 1/3 in., height 15 ft. 7 in., and wing area 1076.4 sq. ft. The P.50-I, weighing 28,600 lb. empty and 44,000 lb. loaded, had a maximum speed of 270 m.p.h. and a range of 1863 miles. It climbed to 13,120 ft. in 22 min. Armament was three 12.7-mm. guns in nose, dorsal, and ventral positions.
The P.50-II weighed 29,040 lb. empty and 44,440 lb. loaded. It had a maximum speed of 279 m.p.h. at 13,120 ft., a cruising speed of 250 m.p.h., a landing speed of 87 m.p.h., a range of 2174 miles, a service ceiling of 25,290 ft., and could climb to 13,120 ft. in 15 min. A total armament of five defensive machine guns was proposed for the P.50-II.