The Fiat G.18 was a twin-engine, all-metal airliner developed in the mid-1930s, representing a pivotal shift for Fiat Aviazione as it entered the era of metal aircraft production. Designed as a commercial transport monoplane, it was placed in a category comparable to the Douglas DC-2 and DC-3. The aircraft served as a technological foundation for subsequent Fiat designs, including the G.12 trimotor and the G.50 fighter.
The prototype G.18 first flew on 18 March 1935. Three original units entered service with the Italian airline ALI (Avio Linee Italiane) in early 1936. These initial aircraft were criticized for being underpowered, though specific engine designations for the original version are not documented in the available sources. To address these performance issues, Fiat introduced the improved G.18V (Veloce) in 1937, delivering six additional aircraft. The G.18V featured a redesigned fin and a long dorsal strake to enhance stability, and was powered by two Fiat A.80 air-cooled radial piston engines producing 746 kW (1,000 hp) each. This improved version reached a maximum speed of 400 km/h and a service ceiling of 8,700 m.
Throughout its civil service, the G.18 operated on European routes for ALI. However, in June 1940, ALI was brought under the control of the Regia Aeronautica (Royal Italian Air Force), and the G.18s were pressed into service as military transports. They were used primarily for troop transport, notably flying troops to Albania in November 1940 during the campaign against Greece. Following the Italian armistice of September 1943, the remaining aircraft were divided: one entered service with the Italian Co-Belligerent Air Force, three were taken over by the Luftwaffe, and one served with the Italian Social Republic (RSI). The RSI-operated aircraft was destroyed on 30 April 1944 after exploding on the runway at Bresso while loaded with munitions.