In July 1935 there flew the prototype of a large wooden twin-float seaplane, powered by three 840-hp (626-kW) Isotta-Fraschini Asso XI inline engines. This was the CRDA Cant Z.505 which had been designed as a mailplane. On 19 August in the same year, Mario Stoppani conducted the first flight of the slightly smaller and lighter Z.506, a 12/14-passenger transport with three 610-hp (455-kW) Piaggio Stella IX radial engines. The type was put into production in 1936 as the Z.506A, and entered service with the Italian airline Ala Littoria during that year on routes around the Mediterranean. Powered by three 750-hp (559-kW) Alfa Romeo 126RC.34 radial engines the Z.506A, flown mostly by Mario Stoppani, set several altitude, distance and speed records in 1936-8, including speeds of 191.539 mph (30825 km/h) 198.7 mph (319.78 km/h) and 200.118 mph (322.06 km/h) over distances of 3,107 miles (5000 km), 1,243 miles (2000 km) and 621 miles (1000 km) respectively. It carried a payload of 4,409lb (2000 kg) to 25,623 ft (7810 m) and 11,023lb (5000 kg) to 22,693 ft (6917 m) and later flew 3,345.225 miles (5383.6 km) over a closed circuit.
A military version, designated Z.506B Airone (heron), was shown at the Milan Aeronautical Exhibition in October 1937. This had a stepped, extensively glazed tandem two-seat cockpit and a ventral gondola which contained the bomb aimer's position and the bomb bay, immediately behind which was a gunner's position. The Z.506B was built at Cant's Monfalcone and Finale Ligure Factories, and by Piaggio under licence. In November 1937 a Z.506B with 750-hp (559-kW) Alfa Romeo 127 RC.55 engines set a load-to-height record of 33,318 ft (10155 m) with a 2,205-lb (1000-kg) payload, and then flew 4,362 miles (7020 km) nonstop from Cadiz to Carevalas. Z.506 variants included an air-sea rescue Z.506S of which at least 20 were produced as conversions from Z.506Bs, and a single Z.506 landplane which was specially prepared with fixed, spatted landing gear for an endurance record attempt by Mario Stoppani; this was at first postponed, then finally cancelled, because of continuing bad weather. In 1936 a heavy bomber prototype, which was essentially a scaled-up version of the Z.506, was built under the designation Z.508. No production version resulted but this aircraft, powered by three 840-hp (627-kW) Isotta-Fraschini Asso XI RC.40 engines, was used to set a number of records, including a speed of 154.26 mph (248.25 km/h) over a 1,234-mile (2oo0-km) course with an 11,023-lb (5000 kg) payload. Last of this family was the Z.509, a larger and heavier version of the Z.506A of which three were built in 1937 for use on Ala Littoria's transatlantic postal service to South America. This model was powered by three Fiat A.80 RC.41 radial engines, and a new wing of 92 ft 11 in (28.32 m) span and 1,076.43sq ft (100.00m2) area was introduced to compensate for increased empty and maximum take-off weights of 22,000 Ib (9980 kg) and 35,200-lb (15965 kg) respectively. Production of the Z.506B totalled 324, including two prototypes which were supplied to the Regia Aeronautica and the Regia Marina; the latter service took over 29 aircraft, the balance of a Polish order for 30 which were not delivered as a result of the German invasion. Five were delivered to the Nationalist forces in the Spanish Civil War late in 1938. A number of the Z.506S air-sea rescue aircraft remained in service until 1959.
Prototype, one built.
Military version, 324 built.
Air-sea rescue version
One aircraft was converted to a landplane for an attempt by Mario Stoppani on an endurance record. It did not take place to due to bad weather.
A larger and heavier version of the Z.506B, three built.
Specifications (Z.506B Series XII)
* Crew: 5
* Length: 19.24 m (63 ft 1.5 in)
* Wingspan: 26.50 m (86 ft 11.3 in)
* Height: 7.45 m (24 ft 5.3 in)
* Wing area: 86.26 m² (928.53 ft²)
* Empty weight: 8,750 kg (19,300 lb)
* Max takeoff weight: 12,705 kg (28,010 lb)
* Powerplant: 3× Alfa Romeo 126 RC.34 radial engines, 560 kW (750 hp) each
* Maximum speed: 350 km/h (190 kn, 220 mph)
* Range: 2,000 km (1,100 nmi, 1,200 mi)
* Service ceiling: 7,000 m (23,000 ft)
o 1 × 12.7 mm (0.50 in) Breda SAFAT machine gun
o 3 × 7.7 mm (0.303 in) machine guns
o 1,200 kg (2,600 lb) of general ordnance or
o 1 × 800 kg (1,800 lb) torpedo