Talks dragged on until the 23rd of August 1944, when Antonescu was arrested and the new government immediately signed a cease-fire agreement and announced the Germans that they had to retire from Romanian soil within the next 24 hours. Hitler, however, had no intentions of abandoning Romania : even after being heavily bombed by the Americans, the oilfields and refineries near Ploiesti still produced over 40% of the fuel the Wehrmacht badly needed. Losing this source was unthinkable, so Hitler ordered his troops to occupy Bucharest and install a puppet regime that would be under complete German control. This order lead to clashes between Romanian and German forces, and a few days later, the former allies had declared war to each other.

The events on the 23rd of August took the ARR somewhat by surprise. Many German and Romanian squadrons shared the airfields, whilst the AA artillery had a lot of mixed units too. It was for many a bizarre moment when their former allies took off or when Romanian pilots left the airfields guarded by German units for the safety of those defended by Romanian troops. On some cases the separation was carried out peacefully, but on others, the situation got tense, as both sides fired on each other as they tried to capture the "enemy's" planes.

In the air, the ARR and the Luftwaffe avoided each other at first, so there is no record of engagements between the 23rd and the 25th of August. But on the 25th, German bombers attacked Bucharest, aiming to hit the royal palace, as a punishment for what they called "treason". When this happened, the ARR did not hesitate to intervene, and that day, Romania declared war on Germany and Hungary. The 7th and 9th Fighter Groups were the first units thrown into action, whilst the ARR commanders sent most of their squadrons on airfields near the city of Craiova, for badly needed repairs and reorganization. On the 8th of September 1944, the Romanian 1st Air Corps was once again ready for action as it was relocated to bases in southern Transilvania to support Romanian and Soviet forces facing the combined German-Hungarian troops aiming to occupy the line of the Carpathian mountains. ARR's last campaign in World War Two was about to begin.

In the days after the 23rd of August 1944, a total of 228 German planes had been captured, but most of them were either undergoing repairs or were just too worn out to be of any use ( 41 were broken down immediately for spare parts, whilst the rest were used for transport or training ). 161 Romanian planes were lost as well, either destroyed by American and Soviet forces unaware of the new situation or captured by the Germans. It wasn't much of a problem, since almost all of them were old fighters and bombers, who had been long since relegated to training duties. The only real loss were the Ju-87 D's of the 6th Dive Bomber Group and the Bf 110s of the 1st Night Fighter Squadron.

When the 1st Air Corps arrived in southern Transilvania, it could field around 20 squadrons with 210 airplanes, half of which were modern German designs. Later on, several more squadrons joined the Corps, boosting its numbers to around 250 planes.

The AA artillery was probably the one branch of the Romanian army who was in excellent shape after the 23rd of August 1944 : thanks to the large amounts of captured German equipment, no less than 10 overstrenghtened AA regiments were ready for action. Organized into 4 independent brigades, these regiments totaled 97 heavy and 77 light batteries, with 420 heavy guns ( Krupp/Rheinmetall 88 mm and Vickers/Resita 75 mm guns ) and 948 light guns. Two of these brigades ( the 1st and the 4th ) were sent to the front and took part to this last campaign until the end.

First clashes between the ARR and the Luftwaffe took place on the 25th of August, when the 7th and the 9th Fighter Groups attacked German bombers sent to bomb Bucharest. Transport planes, like the Ju-52's and the Me-323 Giant's bringing in reinforcements from Yugoslavia, were also engaged, and Lt. Gavriliu of the 1st Fighter Flotilla alone claimed three Ju-52's. Air battles over the capital ended by the 29th, and ARR units began to prepare for regrouping on the other side of the Carpathians. Until the bulk of Romanian squadrons could arrive, only three units ( two observation squadrons with 28 IAR-39's and a single fighter squadron, the 44th one, who had just 9 IAR-80's ) had to maintain air activity. Two IAR-80's were lost ( one shot down by German flak whilst the other one had to crash land due to engine failure ).

Russian AA artillery often fired without warning on Romanian airplanes as they were landing or passing by. Soviet fighters jumped ARR fighters and bombers, although all of them had been repainted according to Russian demands. There are at least three recorded incidents when Romanian planes were shot down by the Soviets. For example, on the 17th of November 1944, six Romanian Ju-87D's were attacked by Soviet Lagg 5 fighters : one Ju-87 was shot down, one more was forced to crash land, and three were seriously damaged. Throughout the attack, the Romanian crews did not fought back, but fired flares and waved the wings according to the day's recognition sign, but it was all in vain. Although ARR's commanders complained to the Soviet 5th Air Army they received no answer. In those early days, pilots didn't feel safe around their "comrades" on the ground either : captain Horia Agarici, who had shot down three VVS bombers in a single day in June 1941, was the "public enemy number 1". On the 9th of September, 1944, the 1st Air Corps entered action in southern Transilvania, in support of the Romanian 1st and 4th Armies and the Soviet 6th Tank Army. On the 13th of September, a combined German-Hungarian offensive was launched aiming to reoccupy the line of the Carpathian mountains. The ARR threw the best units available against this threat : the 6/3rd Dive Bombing Group and the 8th Assault Group attacked enemy units whilst the 9th Fighter Group provided fighter escort. Meanwhile, the 2nd Fighter Group wrecked havoc behind enemy lines, strafing everything that moved on the roads in daylight. Between the 13th and the 17th of September, the ARR returned over the battlefield time after time, until the enemy offensive was stopped for good. More than 40 enemy tanks and many more vehicles were destroyed without losses. There was fierce action in other parts of Transilvania as well, but air engagements were not very frequent, except for the area around the major cities of Cluj and Turda, where about 50 planes from each side clashed in several battles between the 23rd and the 25th of September. The ARR came out worse, with 13 airplanes lost, whilst the Luftwaffe lost just 4. After this battle it was decided to use the IAR-80's and IAR-81's only as fighter-bombers from now on, since it was clear they could not take on the Bf-109's or the Fw-190's. Nevertheless, some IAR pilots did managed to shoot down German fighters, provided they succeeded in tricking the enemy pilot to enter a turning fight, where the superior maneuverability of the IAR-80 made up for its low speed. Several Bf-109's and FW-190's were claimed by the end of the war ( a few were later confirmed ) in these engagements, but these were really exceptions, as against the experienced German aces, who knew the strength and weaknesses of the IAR-80, the Romanian fighter stood little chances.

The ARR lost 64 planes ( 26 shot down by enemy fighters, 17 by flak whilst the rest of 21 were lost in accidents or had crash landed behind enemy lines ).

By early January 1945, the Romanian Air Corps had been redeployed on airfields inside Hungary, preparing its forces to support the massive Soviet offensive scheduled for the 12th of January. Some reinforcements had been received : the 44th Fighter Squadron ( IAR-80 and Bf-109G6 ), the 85th Dive Bomber Squadron (Ju-87D5) and the 60th Assault Squadron (Hs-129B2) had joined the Air Corps together with two Observation squadrons in late September 1944. Also, the 1st and 6th fighter groups had been refitted with Bf-109G's manufactured by IAR, but only the 1st Fighter Group was sent to the front in early 1945. On the 12th, the Soviet offensive kicked off, but the ARR was unable to provide air support due to bad weather. The following day however, all available aircraft took off performing various tasks : from suppressing German artillery and bombing German positions to strafing columns of vehicles and providing fighter cover, the ARR was doing anything necessary.

One of the most difficult missions of the campaign was given to the Romanian bombers on the 11th of January, when they were tasked with destroying two vital bridges over the Danube inside Hungary's capital, Budapest. The VVS had failed to knock out the bridges in spite of several air attacks, so the ARR was called in to do the job. On the 13th of January, 5 Ju-88's of the 79th Bomber Squadron hit the "Lanzhid bridge" ( the Chain Bridge ) while 6 Ju-87D's of the 74th Squadron bombed the "Elisabeth" bridge, scoring four direct hits with 500 kg bombs. Both bridges were destroyed, cutting off the German troops on the east bank from their reinforcements and supply depots.

Romanian planes kept up the pressure until late January, when the Romanian and Russian forces had to stop their advance at the river Hron, inside Slovakia. By this stage of the war, air engagements were all but non-existing, as the Luftwaffe seldom appeared over the battlefields of Slovakia, considered to be a "secondary" front. German flak however, remained a serious threat right until the end of the war.

ARR's last major battle of the war started on the 25th of February, 1945, when the Soviets launched a major offensive aimed at capturing the city of Zvolen. 148 Romanian planes took part in this battle, which was one of the last occasions when they encountered German fighters as the Bf-109G's and K's of the 52 Jagd Geschwader and the Fw-190A's and F's of the 2nd and 4th Jagd Geschwader clashed with the Bf-109G's of the 9th Fighter Group. The ARR lost 6 airplanes ( 2 Bf-109G6 shot down by German fighters and the rest by flak ) claiming one Bf-109K and a Fw-190F ( this kill was confirmed by German sources ). Romanian squadrons remained in action until the 9th of May, 1945 when the war in Europe was officially over. ARR's last victory of the war came on the 7th of May 1945, when a German plane was shot down by a Romanian AA battery at Brno, whilst the last plane shot down was lost the following day, when an IAR-39 was attacked and shot down by a German fighter near Voderady, just north of Brno. One more combat mission was flown even after the war, on the 10th of May, when the Hs-129B's of the 41st Squadron bombed a forest near the city of Uhersky Brod, where some desperate elements from the "Vlasov army" were entrenched, forcing them to surrender. Afterwards, the Air Corps returned home in June 1945, after the last of the 5 campaigns fought by the ARR in World War Two.

Throughout the 9 months of the anti-Axis campaign, the ARR had flown 4307 combat missions, totaling 8542 sorties and over 11300 hours of flight. Over 1360 tons of bombs were dropped and 53 tons of ammunition were fired by all planes. 126 enemy aircraft were claimed destroyed ( the figure includes planes shot down by fighters, by the AA artillery and those destroyed on the ground ) and 228 more were captured during late August 1944, bringing the total to 354 German and Hungarian planes. 83 tanks, 560 various other vehicles, 26 artillery batteries, 15 ships and 92 trains were also listed as destroyed due to Romanian air attacks. ARR losses stood at 176 airplanes lost during the campaign ( shot down by enemy fighters or AA artillery, lost in accidents or because of Soviet "friendly" fire ), plus 161 obsolete trainers destroyed by the Germans in late August 1944. A total of 729 airmen, ground crews and various other personnel were killed or injured during this last campaign.