Germany distributed captured Royal Yugoslav Air Force aircraft and spare parts to Romania, Bulgaria, Finland and the newly created Independent State of Croatia.

The Royal Yugoslav Air Force developed out of the Serbian Aviation Command, which had been created on 24 December 1912, and had been active during the Balkan Wars of 1912–1913.

The next year, 150 Breguet 19 biplane light bomber and reconnaissance aircraft were purchased on credit from the French government, signalling the first significant expansion of the air force.

The Ikarus plant was producing training aircraft and seaplanes using Austrian engines captured at the end of World War I, and imported steel tubing and wire stays.

[10] In 1929, the British military attaché reported that the air force was making slow but steady improvements, but observed that the airfield at Novi Sad was the only one capable of supporting night flying.

The British military attache assessed that the standard of pilot training remained deficient, with a significant number of aircraft being put out of action each year due to accidents.

[14] Steady progress continued to be made in developing the air force, but several weaknesses were evident, including; lack of first-class aircraft, dependence on foreign sources for the bulk of aviation construction material, inadequate repair and maintenance facilities, the slow development of the home-grown aircraft industry, and the negative influence exerted by senior army officers with no aviation experience or knowledge.

The Yugoslav air service was almost entirely equipped with obsolete aircraft, but despite this, the morale of aircrew was good and there was no shortage of young men wishing to fly.

[20] By 1941 the JKRV, with a strength of 1,875 officers and 29,527 other ranks,[21] had over 460 front-line aircraft of domestic (notably the IK-3), German, Italian, French, and British origin, of which most were modern types.

Organized into twenty-two bomber squadrons and nineteen fighter squadrons, the main aircraft types in operational use included seventy-three Messerschmitt Bf 109 E, forty-seven Hawker Hurricane I (with more being built under licence in Yugoslavia), thirty Hawker Fury II, eleven Rogožarski IK-3 fighters (plus more under construction), ten Ikarus IK-2, 2 Potez 630, one Messerschmitt Bf 110C-4 (captured in early April due to a navigational error) and one Rogozarski R 313 fighters, sixty-nine Dornier Do 17 K (including 40 plus licence-built), sixty-one Bristol Blenheim I (including some 40 licence-built) and forty-two Savoia Marchetti SM-79 K bombers.

The Naval Aviation units comprised 75 aircraft in eight squadrons equipped with, amongst other auxiliary types, twelve German-built Dornier Do 22 K and fifteen Rogozarski SIM-XIV-H locally designed and built maritime patrol float-planes.

[22] The aircraft of the Yugoslav airline Aeroput, consisting mainly of six Lockheed Model 10 Electras, three Spartan Cruisers, and one de Havilland Dragon were mobilised to provide transport services to the VVKJ.

The conversion was extremely successful, and experimental aircraft displayed better take-off performance and climb rate than either the standard Hurricane or the Bf 109 E-3 and was only slightly slower than the latter.

Rolls-Royce Merlin III was installed in one of the IK-3 airframes, but this machine had only just been completed at the time of the German attack, and as enemy forces neared Belgrade it was destroyed by the factory workers, together with four other IK-3s undergoing overhaul or modification and a further 25 on the production line.

On 27 March 1941, the overthrow of the government that had signed the Tripartite Pact in Belgrade two days earlier, by a group of officers led by Dušan Simović, an air force general, brought an end to hopes of a settlement with Germany.

[26] On 3 April 1941, Kapetan Vladimir Kren defected in a Potez 25, taking with him intelligence about the Royal Yugoslav Army Air Force, documents that he handed over to the Germans.

Captain Ihlefeld, who was credited with over forty air victories, was shot down by Corporal Vlasta Belić, firing a Darne machine gun, caliber 7.7 mm, taken from a Yugoslav Breguet 19.

Several VVKJ aircraft escaped to Egypt via the Kingdom of Greece, and the crews then served with the British Royal Air Force (RAF).

In 1940, Britain attempted to bring Yugoslavia to the Allied side by supplying military aid to the Royal Yugoslav Air Force, including new Hawker Hurricane fighter aircraft.

After Yugoslav Prime Minister Cvetković signed the Tripartite Pact, his regime was overthrown by a military coup d'état two days later, Fascist Italy demanded that their ally Nazi Germany invade Yugoslavia in order to reach Greece and help their disastrous campaign there and in the process break up Yugoslavia since Italians were laying claim on certain territories (mostly Dalmatia).

However many of these airfields lacked facilities and had inadequate drainage which prevented the continued operation of all but the very lightest aircraft in the adverse weather conditions encountered in April 1941).

[29] The bomber eskadrilla (the equivalent of 22 squadrons) and maritime air force hit targets in Italy, Germany (Austria), Hungary, Romania, Bulgaria, Albania and Greece, as well as attacking German, Italian and Hungarian troops.

Meanwhile, the fighter eskadrilla (the equivalent of 19 squadrons) inflicted not insignificant losses on escorted Luftwaffe bomber raids on Belgrade and Serbia, as well as upon Regia Aeronautica raids on Dalmatia and Herzegovina, whilst also providing air support to the hard pressed Yugoslav Army by strafing attacking troop columns in Croatia, Bosnia, Macedonia and Serbia (sometimes taking off and strafing the troops attacking the very base being evacuated).

It must, however, be noted that between 6 and 17 April 1941 the VVKJ received an additional 8 Hawker Hurricane Is, 6 Dornier Do 17Ks, 4 Bristol Blenheim Is, 2 Ikarus IK 2s, 1 Rogožarski IK-3 and 1 Messerschmitt Bf 109 from the aircraft factories and workshops.

[31] Some 70 or so operational and training aircraft succeeded in escaping to Greece and 4 to Russia (8 Do 17Ks and SM.79Ks set out, but half were lost due to poor weather conditions, mountainous terrain and/or overloading).