As a result of experiences from the Korean War alongside newly developed concepts of aerial cooperation, the members of NATO recognised a need to reequip their inventories with suitable jet-powered ground attack aircraft.

The competition was intended to produce an aircraft that was light, small, expendable, equipped with basic weapons and avionics and capable of operating with minimal ground support.

The specified technical requirements included a 1,100 m (3,610 ft) takeoff distance over a 15 m (49 ft) obstacle, the capability to operate from semi-prepared grass airstrips and roads, a maximum speed of Mach 0.95, a range of 280 km (170 mi) with 10 minutes over the target while possessing a maximum of 2,200 kg (4,850 lb) empty weight and 4,700 kg (10,360 lb) max weight.

[2] The challenge of providing an engine that matched the requirements of lightness and power, reliability and ease of maintenance was solved by using the Bristol Siddeley Orpheus turbojet then at the start of development in the UK.

[3] On 18 March 1953, these submitted designs formally began to be assessed by the AGARD committee, which was under the chairmanship of Theodore von Kármán.

[2] On 9 August 1956, the prototype G.91 conducted its maiden flight at the Caselle airfield, Turin, Italy; it was flown by Chief Test Pilot Riccardo Bignamini.

On 20 February 1957, during a test flight intended to explore the limits of the aircraft's speed-load envelope, difficulties led to the destruction of the first G.91 prototype.

[2] The re-engineering work that had been performed to cure the vibration problem was very extensive and resulted in the second prototype being fitted with a larger tail, a six cm (two in) higher canopy, and the addition of a ventral fin.

[3] In September 1957, at the Centre d'Essais en Vol at Brétigny-sur-Orge, in France, the three rival aircraft types met for evaluation trials.

[17] The German order involved a production run of 294 G.91s that were domestically constructed in Germany under a license production arrangement by Flugzeug-Union Süd, a consortium of former competitors Messerschmitt, Heinkel and Dornier; Messerschmitt produced the forward fuselage and tail assembly, Dornier manufactured the center fuselage along with final assembly and flight testing, while Heinkel fabricated the wing.

[20] However, the service subsequently relinquished all fixed-wing aircraft operations to the United States Air Force, and thus the prospective G.91 procurement was not pursued.

[2] A key function of the aircraft is its short-field capability, having been constructed with a rugged airframe to withstand the demands imposed by high-intensity operations and the use of semi-prepared airstrips; the undercarriage is furnished with low-pressure tyres for the same purpose.

[23] The center fuselage section houses the armament bay, which is set beneath the cockpit, and the seven split fuel tanks, which are protected against damage from ground fire by armour plating.

Other munitions included various rockets and bombs; while gun pods and external drop tanks can be installed on hardpoints fitted on the wing.

Both weapons and ammunition in the armament bay were mounted on panel doors, which could be easily removed and quickly swapped by two men during rearming on the ground.

[23] In addition, various access panels are incorporated to enable simple field maintenance duties to be readily performed on the type.

[2] The G.91 is equipped with a swept wing, which uses an all-metal two-spar structure; the outer panels can all be detached for transportation or easy replacement, while the center section is integral with the fuselage.

[19] The tailplane is electrically actuated and had irreversible hydraulic elevators fitted with an artificial feel system as well as hydraulically-actuated air brakes and a drogue parachute located at the base of the rudder for rapid deceleration.

[19] For the purpose of readily carrying out operations from austere airstrips, Fiat developed purpose-built ground support equipment for the easy and rapid servicing of the aircraft.

Specifically, the equipment needed to inspect, maintain, resupply, and repair the G.91 were designed to possess minimal weight and size to facilitate transportation.

In 1959, the 103Mo were transferred to Frosinone Airport for trialling the austere basing capabilities of the G.91, including operating from various types of terrain.

[19] The unit also performed exercises in the vicinity of Venice, such as at Maniago and Campoformido, in the presence of NATO officials; during this stage of the trials, German pilots also flew the aircraft.

[16] An initial five G.91R/3 aircraft were delivered to Erprobungstelle 61 for trials with subsequent deliveries being allocated to Aufklärungsgeschwader 53 (53rd Reconnaissance Group) based at Erding, near Munich along with Waffenschule 50 (Weapons School 50).

[16] The G.91R/3 equipped four newly formed Leichte Kampfgeschwader (light attack wings), often being used to replace older aircraft such as the American-built Republic F-84F Thunderstreak.

[29] During the early 1980s, the G.91 R/3 was replaced in German service by the Dassault/Dornier Alpha Jet which operated in the same role;[35] the last G.91 aircraft were officially retired in 1982.

[36] From 1961, Portugal became involved in fighting against nationalist movements in its African overseas territories, the series of conflicts becoming known as the Portuguese Colonial War.

In 1965, as the scale of fighting increased, Portugal attempted to purchase 100 surplus Canadian built Sabre Mk 6s from West Germany, but instead, it was offered 40 G.91R/4s,[38] which had originally been built for Greece and Turkey and which differed from the rest of the Luftwaffe G.91s sufficiently to create maintenance problems in exchange for allowing Germany to build and use an airbase at Beja in Portugal for training.

[37][39] G.91s arrived in Portuguese Guinea in 1966, equipping Esquadra 121 Tigres based at Bissau, and being used for reconnaissance and close support with rockets, napalm and bombs against PAIGC rebels.

[40] When the PAIGC started to be supplied with Soviet-made Strela 2 (NATO designation SA-7 Grail) MANPADS in early 1973, these immediately became a threat to Portuguese air superiority.

An attempt was then made to acquire more Fiat G.91s from Germany by having Dornier disassembling the aircraft and then selling them as spare parts to Switzerland and Spain.