On 20 February 1958, the first pre-production G.91 conducted its maiden flight. In August 1958, the 103mo "Gruppo", 5a "Aerobrigata", called ""Caccia Tattici Leggeri"" (Light Tactical Fighter Group), was formed for the purpose of conducting operational evaluation of the aircraft, initially based at Pratica di Mare Air Force Base. 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. 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.