On the outbreak of World War II , the French Air Force was in the middle of a modernization and rearmament process which had started in early 1938. When hostilities opened, the Air Force, which had never been so under equipped as during the Munich crisis, could make use of a partly revamped fighter force. The bomber force however was in dire straits, with only a few modern front-line aircraft available.

The vigorous efforts made during the 'Phoney war', combined with an increasing industrial
production, did not suffice to help the Air Force overcome its original handicap. Admittedly, both aircraft and engines were being produced at a good pace, but flying was restricted due to shortfalls in equipment and spare parts.

To top it all, the ill conceived command structure further impaired efficiency, the Air force being broken into several commands, namely the earmarked forces (fighters, bombers, and strategic reconnaissance aircraft) who were directly answerable to the Commander-in-Chief, Air Forces, and the structural forces (surveillance aircraft which amounted to 50 % of total assets) under the control of the ground forces. Compounding these command problems was the fact that part of the earmarked fighters were disseminated amongst the ground forces and were therefore wholly cut off from their parent service.

When the Battle of France started on 10 may 1940, the Air Force joined in the air battle and performed support missions with its bombers as well as interception of German aircraft over the front line. Moreover, it was also tasked with an air defence mission in order to safeguard the armed forces as well as the inner area. With a mere 650 fighters (MS 406, Bloch 152, Curtiss H 75, and Dewoitine 520) and a few dozens of modern bombers the pilots were soon unable to cope. All the more so as the number of available aircraft dropped sharply in the raging inferno of combat.

Crippled by a lack of signals equipment and the progressive loss of watch posts, unable to provide troops to join in the battle, relentlessly called on by the retreating Army hotly pursued by the German Panzers, the Air Force soon ran out of resources. By mid June 1940, as France was about to collapse, General VUILLEMIN, Commander-in-Chief, Air Forces, ordered the transfer of all the modern aircraft to North Africa. Upon signature of the armistice, the spearhead of the French Air Force was gathered across the Mediterranean Sea. It consisted of hundreds of fighters and bombers whose efficiency was nevertheless impaired by the command structure which was in complete disarray as well as by serious difficulties in resupplying spare parts and fuel oils.

According to the very terms of the armistice, the Air Force should have been disbanded once all the aircraft were moth-balled in storage areas under the control of German and Italian committees. However, the situation was completely disrupted when the British Fleet raided Mers-El-Kebir naval base on 3 July 1940. As the Germans realized that the French could still manage to protect their colonies with their own forces, they decided to postpone the disbanding of the French Air Force as a result of which the Vichy regime was allowed to maintain important forces that were in charge of the defence of the mainland as well as the colonial empire, from 1940 to 1942.

Parallel to the Vichy regime's Air Force, Free French Air Forces were getting organized as early as July 1940, with at the beginning a mere 500 men. The very few crew and aircraft making up this force fought within British air units in East Africa, French equatorial Africa, Libya, Egypt, and even Crete.

The Free French Air Forces took on a permanent structure under the aegis of General VALIN – who joined De GAULLE in 1941 with fighter, bomber and coastal defence squadrons. These units were given the names of French provinces as a reminder of occupied France ; "Alsace", Ile de France", "Lorraine", "Bretagne", "Artois" and "Picardie".

In the meantime, spurred on by the leader of Free France, a fighter squadron was sent to the Soviet Union where it was to be the only French military unit to engage the enemy. First named Normandie, the unit next composed of two squadrons, was then named Normandie-Niemen regiment during the last quarter of 1944.

When the Free French Air Forces merged with a hard core of units still stationed in North Africa after the allied landing in 1944, a new French Air Force was born. After being rearmed by the US and Great Britain as part of Scheme VII, the French Air Force gradually engaged the enemy under the command of General BOUSCAT assisted by his vice chief of staff General VALIN.

With the progressive integration of squadrons into allied major air commands the new Air Force got organized little by little. As early as 1943-1944, the first fighter and bombing wings equipped with Spitfire, P-39 Aircobra, P-47 Thunderbolt, B-26 Marauder, were created. The allies also allowed the Algiers based authorities to set up reconnaissance units equipped with P-38 Lightning and P-51 Mustang. Meanwhile, on British soil, heavy bombing units the Guyenne and Tunisia squadrons came into existence. The aim was to integrate them into the RAF's Bomber Command.

The French Air Force performed coastal defence missions in the Mediterranean and also took part in the operations over Corsica (late 1943) and Italy (early 1944) and Many French air units were successfully deployed in Operation "Overland" in Normandy and in Operation "Anvil Dragoon" in Provence.

In October 1944, after the pilots from North Africa and those from France had united, the Air Force commanders decided to form a greater air unit including most of the fighter and bombing squadrons that had come from North Africa. The 1st French Air Corps, under the command of General GERARDOT, embodied the gradual progress towards operational autonomy of the Air Force that should have led in 1945, had the war gone on in Europe, to the creation of a full-fledged French Air Force. It would have been composed of the 1st French Air Corps, the Atlantic air forces that fought against the German pockets of resistance on the French coastline and the Free French air units that were deployed in Northern Europe to assist the British forces.

In May 1945, when the war came to an end in Europe, the French Air Force probably reached an apex of power that was never to be equalled, with more than 150,000 men and some 40 fighter, bombing, reconnaissance and transport squadrons.