As French resistance to the German advance began to collapse, between the 18th and 20th of June, GC I/3, II/3, III/3, III/6, and II/7 flew their aircraft to North Africa. 153 machines remained behind in unoccupied France. Three D.520s of GC III/7 escaped to Britain and were incorporated into the Free French 1st Fighter Group formed at RAF Odiham.
After the Armistice, the German victors allowed the Vichy government to maintain a reduced air force. Under the terms of the agreement, no D.520 unit was to remain in service on the French mainland, and all surviving D.520 aircraft in France were dispersed and stored. In North Africa, GC I/3, II/3, III/6, and III/7 as well as Aeronavale Escadrille 1AC and 2AC(the former AC1 and 2) were allowed to remain in service with their D.520s.
In April 1941, the German authorities agreed to allow the resumption of aircraft manufacture in unoccupied France. When SNCAM was dissolved, its plants were absorbed by S.N.C.A. du Sud-Est (SNCASE). The Vichy Air Force adopted the D.520 as its standard fighter, and the German Armistice Commission permitted production of the D.520 to resume at Toulouse-Blagnac. 550 D.520s were ordered on June 23rd. They were to replace all other single-seat fighters in service in Vichy, and in a second stage of the program, the D.520 was to equip newly-formed units. By the middle of 1943, it was anticipated that the Vichy government would be able to field an Armistice Air Force equipped with 17 D.520-equipped Groupes with 442 front-line aircraft, three Aeronavale Escadrilles with 37 aircraft, plus 3 training units with 13 aircraft.
The first batch of 22 aircraft was delivered in August of 1941. In 1942, the D.520 number 465 was flown with an improved Hispano-Suiza 12Y-45 engine, a modified radiator, and inboard hinged wheel doors. By December 31, 1942, 349 aircraft had been delivered, 197 of which were powered by the 12Y-49 engine. This brought total production of the D.520 to 775 aircraft.
By October of 1942, nine Vichy Groupes de Chasse had been equipped with the D.520. In addition, the 1o Flotille de Chasse had been equipped with the D.520. Vichy D.520s saw some action against British forces in the Levant and had escorted Vichy bombers in an attack on Gibraltar.
GC III/6 and II/3 took part in operations in Syria in June-July 1941. They were later joined by Escadrille 1AC. During that operation, they saw combat against RAF aircraft. GC III/6 was credited with 19 confirmed kills and four probables. GC II/2 was credited with three confirmed kills and two probables. Esc. IAC was credited with eight kills. Vichy D.520 losses totaled 32, with 11 being shot down, 12 lost in accidents, 7 being destroyed in the ground, and two being abandoned in Syria when the fighter units flew back to French North Africa.
At the time of the Operation Torch Anglo-American landings in North Africa in November of 1942, 234 D.520s were in unoccupied France (of which 93 were in service), 173 were in North Africa, and 30 were in Senegal. French-based D.520 units comprised GCs I/1, II/1, and III/9 (which had recently received the D.520 in place of its Bloch 152s), and I/2. GC I/2 escaped with 24 aircraft to Meknes on November 9 to avoid capture by German forces. In North Africa, D.520s equipped GCs II/3, III/3 (formerly I/3, its designation being changed at German request since three of its pilots had fled to Gibraltar on October 14, 1941), III/6, II/7, and II/5 Aeronavale IF Flotille (comprising Escadrilles 1AC and 2AC) was also based in Africa.
The Allied landings gave rise to fratricidal air battles in which the D.520s of GC III/3 and II/5 were involved, as well as those of 1F Flotille and the Hawk 75s of GC I/5 and II/5. Losses were heavy on both sides. The Aeronavale lost 19 Dewoitines and seven Martin bombers, and the Armistice Air Force lost 16 D.520s and Hawks. Allied air forces lost 44 aircraft during these clashes.
In response to the Allied landings in North Africa, German forces invaded Unoccupied France in November of 1942. On November 27th, all French armed forces were disbanded and all existing D.520s were seized. This included 246 D.520s serving with Vichy units, plus 169 D.520s in various stages of completion at SNCASE.
Some of these seized D.520s were transferred to two Luftwaffe fighter training units (JG-103 and JG-105). They were highly praised by Luftwaffe crews for their exceptional maneuverability. However, the accident rate was fairly high owing to the great differences between it and the German aircraft to which the pilots were accustomed.
Sixty D.520s were transferred to the Regia Aeronautica, and were operated primarily as fighter trainers by Gruppi 13, 22, 24, and 167. About a hundred D.520s were issued to the Bulgarian Air Force, which used them operationally against the US 9th Air Force. Most of these were lost in combat. The Rumanian Air Force operated a small batch of D.520s in combat on the Eastern Front, flying them alongside that air force's Bf 109s.
Upon the liberation of Southwestern France, a French FFI (Forces Francaises de l'Interieur) fighter Groupe was formed with D.520s that had been captured from the retreating enemy. This unit took part in attacks on retreating German units and provided escort for Allied bombers and strafed artillery positions. In March of 1945, this unit reequipped with the Spitfire Vb, and its D.520s were transferred to GC B I/18 and to a training unit. About 55 D.520s were recovered from the Luftwaffe as the Allied forces advanced eastward, which were later reinforced by another 20 which were brought back from North Africa.
In postwar years, the D.520 continued to serve with training units in the revived Armee de l'Air. Several were converted to two-seat configuration under the designation D.520 DC (for "double commande"). The last unit to fly the D.520 was the Escadrille de Presentation de l'Armee de l'Air (EPAA), which had previously flown Yak 3s brought back to France from the Soviet Union by the Normandie-Niemen regiment. The last D.520 was finally withdrawn from service in September of 1953.
Four D.520s are known to exist ca 1966. No. 408 belongs to the Musee de l'Air, No. 603 is on display at the Ecole de l'Air, No. 650 (a DC) is on display at Etampes-Mondesir, and No. 862 is on display at the Luxeuil-Saint Sauveur Air Base.
