The Farman F.221 was the first four-engined bomber to enter service with the French Armée de l'Air, and was still in service in small numbers at the start of the Second World War.
The F.221 was developed from the prototype F.220, which made its maiden flight in May 1932. Like the F.220, the new aircraft was built around an angular fuselage. It had a high-mounted wing with a wide chord (distance between leading and trailing edge). The central section of the wing had parallel edges, while the outer section tapered slightly. The four engines were carried in two nacelles mounted on stub wings attached to the lower fuselage. Each nacelle carried one pusher and one puller engine. The fixed undercarriage was attached to the nacelles.
The prototype F.221.01 differed from the F.220 in several ways. The inline engines of the earlier aircraft were replaced with 730hp Gnome-Rhone 14Kbrs Mistral Major radial engines, with cowling for the front engines only. The F.221 kept the 'stepped' nose of the earlier aircraft, but the front gunner's open balcony replaced with an enclosed gun position. The same was done to the open dorsal position, giving the F.221 two .303in guns in enclosed positions and one ventral .303in gun in a semi-retractable turret. In August 1935 the prototype was returned to Farman, where it was given a retractable undercarriage and became the prototype F.222.01.
The F.221.01 made its maiden flight in May 1933. Early in 1934 more powerful 800hp Gnome and Rhone 14Kdre engines were installed, and a batch of ten F.221.1 production aircraft were ordered. The production aircraft saw the enclosed nose and dorsal gun positions replaced with manually operated turrets, and the rear engines were given cowlings.
The ten production aircraft were delivered between June 1936 and January 1937, and were used to equip the 15th Escadre de Bombardement, a unit that had been formed to operate the new aircraft in July 1935. This made France the second nation to have an operational four-engined bomber, following the Soviet Union, where the Tupolev TB-3 was in service in much larger numbers.
By the start of the Second World War some of the F.221s were still in front line service, and from December 1939 they took part in the leaflet dropping campaign over Germany. Most were soon moved to transport units, but at least one was used in a frontline role after the German offensive in the west began in May 1940, for F.221 No.3 was lost on 19 May when it caught fire after bombing German troop concentrations.
A small number were in Indo-China when the Japanese invaded Tonkin in September 1940. They took part in the three days of intermittent fighting that followed before the Vichy government agreed to Japanese occupation of the area.
Most of the remaining F.221s remained with GB 15 when it became Groupes de Transport GT 15. They were based in North Africa after the fall of France, but some were in Syria during the Allied invasion in the summer of 1941.