Caproni Ca . 133 The Caproni Ca . 133 was a three - engined transport / bomber aircraft used by the Italian " Regia Aeronautica " from the Second Italo - Abyssinian War until World War II . Originally developed as a civilian airliner and successor to the Ca . 101 , the Ca . 133 prototype first flew in December 1934 , and production began in 1935 . The military versions of the aircraft were used as transports and light bomber s and saw action on all fronts . Design . Designed by " ingegnere " Rodolfo Verduzio , the Caproni 133 was aerodynamically and structurally an improved Ca . 101 . Like its predecessor , the Ca . 101 , was a robust and inexpensive aircraft , designed to be easily maintained in difficult conditions and economical to operate . It had a welded steel - tube structure , mixed construction , with metal and fabric covering , main wheel spats , flaps and modified tail surfaces . The wing was high - mounted , roughly elliptical , and made of wood and steel . The undercarriage was spatted and fixed . The aircraft was powered by three engines , one in the nose , and one under each wing mounted in faired nacelles , with NACA cowlings , supported by steel tubes . The civil version could accommodate up to 16 passengers . It was used by Ala Littoria . The military version was widely used by Regia Aeronautica , mostly in Italian East Africa . As a bomber it incorporated two small internal bomb bays where it could hold up to 500 kg ( 1 , 100 lb ) . Larger ordnance could be mounted externally . It was armed with four 7 . 7 mm ( . 303 in ) Vickers machine gun s , one dorsal , one ventral , and two lateral . Bomber aircraft operated as military transport , redesignated Ca 133T , had the interior modified to accommodate 18 fully equipped soldiers . Operational service . Second Italo - Abyssinian War ( 1935 – 1936 ) . The Ca . 133 was well - suited for colonial use , and it became the most successful of all Italian colonial aircraft . The more advanced Savoia - Marchetti SM . 81 s were too valuable to be used in ' low level wars ' and were also more costly . The war was thus fought mainly with the Ca . 101 , Ca . 111 and Ca . 133 . Around 100 Ca . 133s took part in the conflict , and as well as ' normal ' bombing and strafing , they were often equipped with mustard gas and Phosgene chemical bombs . These weapons were forbidden by the Geneva Protocol of 1925 , but in this war ( and in Libya ) the Italians ignored the convention . The Ca . 133s were also used as transports to support the army , as well as reconnaissance aircraft . Without any air opposition , and flak almost exclusively based on small - calibre arms , air power was a decisive factor in Italy ' s final victory , culminating in the capture of Addis Ababa in early 1936 . Even so , COIN ( COunter INsurrection ) operations continued until the start of World War II . Spanish Civil War ( 1936 – 1939 ) . While in Ethiopia they were widely used , in Spain the Ca . 133 was found to be too slow , and highly vulnerable to enemy Polikarpov I - 15 and I - 16 aircraft , and to heavy anti - aircraft fire . World War II ( 1939 - 1945 ) . The " Regia Aeronautica " soon realized that despite its improvements , the type was suitable only for colonial use in North and East Africa . At the outbreak of war the Ca . 133 equipped 14 " Squadriglie da Bombardamento " in these theatres . In mainland Italy , the Ca . 133 was used mostly as a light transport aircraft supporting fighter and bomber squadrons by carrying supplies , personnel and spare parts . In East Africa , in the first days of combat , it was still used as bomber and attack aircraft . On 12 June 1940 , in the south region , three Ca . 133s of 66a " Squadriglia " from Yavello attacked an Allied column of half a dozen trucks and 200 men . Ca . 133s of 65a " Squadriglia " , from Neghelli , attacked the Allied positions around Moyale on two occasions , each time with three aircraft . That night , ten Caproni Ca . 133s bombed the port of Aden and Khormaksar airfield , already attacked , during daylight hours , by seven SM . 81s of 29° " Gruppo " . Three other Capronis attacked Cassala airfield in the Sudan . It was also used as an air ambulance in the Ca . 133S ( Sanitary ) variant . Over 250 Ca . 133s were in service in September 1939 , when the war broke out . Some survived until the Armistice in 1943 . Post - war . A handful were retained for civilian service with the airline " Ala Littoria " . Some were exported to Austria . The last Ca . 133 was phased out by the " Aeronautica Militare " in 1947 , and the last Ca . 148 flew until 1956 with the Italian Aeroclub .