Jugoslav Partisan Aviation: Because of the guerilla nature of partisan warfare, there were little prospects for the Jugoslav partisans to form their own aviation, although there were some cases when supporters of the National Liberation Struggle escaped along with their planes from the Croatian Air Force to the partisans. After two unsuccessful attempts at the end of 1941, the pilots Franjo Kluz and Rudi Cajavec, with his mechanic Milos Jazbec, managed to defect to the partisans. They escaped on 23 May, 1942, with their planes Potez 25 (Franjo Kluz) and Breguet 19 (Cajavec and Jazbec) from Banja Luka (north-western Bosnia) to the recently liberated town of Prijedor. These two defections symbolize the beginning of the Jugoslav partisan aviation. From the airfield in Prijedor and from another airfield near the village of Medjuvodje (near Kozara), these two partisan pilots took off on 4 June, 1942, on their first sortie against the enemy. Kluz was accompanied by his mechanic Mitrecic, and equipped his (until then) un-armed Potez with a machine gun "Sarec" as well as with some pipe bombs (to be dropped by hand) that were produced by partisans at the "Ljubija" Mine (the largest iron ore mine in all of Jugoslavia). Cajavec was killed during the first mission, when he flew too close to the Banja Luka Airfield and town. He was wounded and forced to land near the village of Kadinjani. In order to avoid capture he shot himself. His mechanic, Milos Jazbec, was captured and later executed in Zagreb. Kluz managed to complete three more missions, during which he attacked with his machine gun and pipe bombs enemy transport columns and garrisons. On 6 July, 1942, his plane was spotted and destroyed on the ground by a German fighter at the airfield near Lusca Palanka.

Until Italy's capitulation in September of 1943, the partisans were unable to form any new air force. This changed after the Italian capitulation. The partisans captured at the airfield at Gorica quite a large number of planes, from which one was successfully used by the Operative Headquarter of the Primorska Zone (Operativni Stab Primorske Cone in Slovene), while two other captured planes were incorporated into Air Base of Main Headquarter for Croatia. Especially interesting is the story of one small seaplane fleet of the Royal Jugoslav Naval Air Force which was captured by the Italians during the April War of 1941, and then remained untouched at Divulje until the Italian capitulation. Partisans captured the seaplanes together with a small support ship, and hid the fleet during the day in various bays near Trogir or some liberated Adriatic islands. By night the partisan naval pilot named Ciril Vrabic had flown, between 11 September and 6 October of 1943, some 30 missions. During the missions he usually observed enemy moves on both land and sea, but he also transported messangers and attacked enemy columns and bases from Neretva Valley to Sibenik. In October and November of 1943, two other planes from the Croatian Air Force defected to the partisans. One of them was later used for training of personnel of 1. Air Base of NOVJ (Jugoslav National Liberation Army), while the second plane (a Do-17 bomber) was assigned the task of taking a delegation of the Supreme Headquarter of Jugoslav Liberation Army to the Allied Command in Italy. Unfortunetly the plane was spotted just before take-off from the Glamocko Polje Airfield and destroyed by a German recon plane. This took place on 27 November, 1943, and Ivo Lola Ribar was killed in this attack (he was a member of the Central Committee of the Communist Party of Jugoslavia since 1940, a member of the Committee's Political Bureau since 1941, and the leader of the Jugoslav Communist Youth Association).

On 18 August, 1944, on the liberated Adriatic island of Vis was formed a Liaison Squadron. This squadron performed mostly liaison functions between the Supreme Headquarter of Jugoslav Army and its units on the battlefields/front-lines. Until November of 1944, when the squadron was moved to Belgrade, it performed 1 200 missions/sorties. This squadron had some minor one-engine planes as well as one Junkers Ju-52 which was captured at Niksic, Montenegro. A second Jugoslav partisan aviation unit was similar to the Liaison Squadron; it was the Squadron of the 5-th Corps of NOVJ, which was formed on 21 September, 1944, from planes captured at Zaluzani Airfield near Banja Luka. This new squadron consisted of a couple of Morane MS406 fighters, as well as of two-engine Caproni planes, some Bcker training planes, and BE-51 sport planes. These aircraft participated in their first action on the very same day when the squadron was formed! They participated in an attack on the Banja Luka Fortress, where surrounded Ustasa units fought very hard. When the Germans later pushed the partisans out of Banja Luka, the squadron was moved to other airfields in western and eastern Bosnia. It performed 90 combat flights, and captured two more planes; a Junkers Ju-87 and an FP-2. During all this time the squadron was supplied with fuel, ammunition, and other essentials, only from the areas which were under control of the 5-th Corps of NOVJ; this proved that aviation can even be used by partisans themselves in the conditions of partisan warfare. This squadron's successes in battle were never any great, nevertheless, its actions were a tremendous boost of morale for the partisans and civilians on the ground.

Regular Jugoslav Partisan Air Force: Italian capitulation in September of 1943 combined with Allied landings in Italy, made it possible to form new and regular partisan air force units, which of course dependet mainly on Allied material and operative support. In October of 1944, the Supreme Headquarter appealed through the "Free Yugoslavia" Radio Station to all the Jugoslav pilots in the Near East (Egypt) and in the Croatian Air Force to join the Partisan Air Force. All those who responded gathered in Livno, where on 14 October, 1943, was formed the 1-st Air Base of NOV (National Liberation Army). Soon gathered about 60 pilots and, after an agreement with the Western Allies, they were transferred to Bari (southern Italy) at the beginning of January, 1944. There began the basic air training of more than 220 Jugoslavs.

At the beginning of March 1944, all pilots were transferred by ships to North Africa. On 22 April, 1944, on the Benina Airfield near Benghazi (northern Libya) was formed RAF Command First Yugoslav Fighter Squadron (or in RAF's own records the 352-nd RAF Squadron). On 1 July, 1944, was formed the Second Yugoslav Fighter Squadron (the 351-st RAF Squadron). Following intense training, they were given 16 Spitfire V and 16 Hawker Hurricane IV planes. These units contained several ex-Royal Jugoslav Air Force pilots who until now served in various U.S. and British air force units. An agreement was concluded between the Western Allies and the partisans, which stipulated that these two units confine their area of operations exclusively to Jugoslavia.

The Spitfires of the First Squadron made their first combat flight on 18 August, 1944, from Canne Airfield in Italy. They took-off under the command of their Squadron Commander Milet Protic. They flew over the Adriatic Sea to Peljesac Peninsula, where they attacked German coastal positions. Until the end of the war, the squadron made 364 combat missions with about 1 208 flights. In the process they suffered heavy casualties: from the 21 pilots who completed the training in Lybia seven were killed; German anti-aircraft artillery managed to shoot-down nine planes and damaged four other ones.

The Second Squadron underwent special training with the use of rocket missiles, which were at that time the standard armament of the Hurricane fighters. It made its first combat flight on 13 October, 1944. Until the end of the war, the squadron performed 978 combat flights during which it attacked various enemy columns, ships, and artillery positions. They also frequently supported NOVJ infantry in its operations on the ground. Three pilots were killed and the squadron lost nine planes.

The earliest sorties were conducted from the bases in Italy, but soon both squadrons moved to the liberated Vis Island on the Adriatic Sea. Later, in the beginning of 1945, they were both moved to the Skabrnje Airfield near Zadar (central Dalmatian coast). These moves increased the aircraft's reach further into Jugoslavia. The damages inflicted on the enemy by both squadrons were very high; the destroyed enemy equipment included over 270 motor vehicles, 29 locomotives, 172 railway carriages, 52 various seagoing targets (like ships, tugboats, and etc.), and 100 other vehicles. Six railway stations, two bridges, and one power plant were also destroyed.