No need to get hostile...
28.9.1939 Hawk 75 near Tündorf by Joseph Bürschgens (who was wounded)
7.11.1939 Blenheim near Opladen by Joachim Müncheberg
18.12.1939 6 Wellington bombers + several damaged near Wilhelmshaven, first by Johannes Steinhoff himself, no losses
Thats 8-0 during the sitting war, they didnt take part to Case White (Poland).
10.5.1940 5 wins against Dutch fighters while escorting Ju 52s. Wolfgang Ludewig ordered to land near Haag and find out where the paratroopers are, plane damaged by anti-aircraft fire so he couldnt fly back
11.5.1940 26 of GC I/4 Hawk 75s against JG26 near Antwerpen, 6 confirmed victories to no losses (4 French pilots KIA or WIA), many more Hawks damaged
11.5. later same day against GC/III/1 and GC III/3 MS.406 fighters near Antwerpen, 1 confirmed victory, feldwebel Gerhard Hertzog shot down and captured, later sent to Canada
13.5. against 264. Squadron Defiants and 66. Squadron Spitfires when escorting Ju 87 Stukas near the Dutch coast, 5 Defiants and a Spitfire shot down(cross-checked, true casualties), Karl Borris shot down, bailed out and walked to home
13.5. near Moerdijik, Fokker T-V and Fokker G-1 shot down by Karl Ebbighausen
13.5. against GC III/3 MS.406s near Breda, 1 shot down by Eberhard Henrici, 2nd one collided with Hermann Speck while a second Bf 109 was shot down but the pilot survived
16.5. First time over France.
18.5. afternoon, large furballs over German armor spearhead heading towards the Channel, 10 MS.406, 1 Hawk 75, 1 Hurricane. A Bf 109 was shot down, pilot captured by the French but released (!!!) 3 days later!!!!!!!
19.5. II/26 scored 3 wins, Captain Herwig Knüppel MIA, found dead 2 days later
24-27.5. 10 wins to no losses when operating from Antwerpen and Western Belgium
28.5. Operation Dynamo, evacuation of Dunkerque, begins:
28.5. I/JG26 over Dunkerque, 6 victories to 1 loss against Spitfires.
28.5. II/JG26 over Dunkerque, 2 Spitfires, 1 Hurricane
28.5. III/JG26 over Oostend, 6 Hurricanes confirmed
29.5. bad weather cleareed only late in the afternoon, against massive formation of mainly Spitfires near Dunkerque, 4 Spitfires shot by II/JG26 while III/JG26 got 6, mixture of Hurricanes and Spitfires. The RAF was after Ju 87s (none were lost) and managed to get themselves bounced by the Bf 109 escorts. No Bf 109 losses. (RAF claimed 15!!)
30.5. fogged in, no flights
31.5. over and near Dunkerque again, I/JG26 scored 1-2 against Spitfires, II/JG26 bagged a Hurricane. III/JG26, escorting bombers, managed to again bounce on the British fighters and shoot down 1 Defiant (2 others collided and went down on their own), 5 Hurricanes(confirmed cross-checked losses), 2 Bf 109s lost.
1.6. 6 pilots and 8 Bf 109s lost against the RAF mainly, 5 Hurricanes shot down cross-checked(6 German, claims, 3 were later confirmed)
2.6. again escorting bombers, 6 RAF fighters shot down near Dunkerque to no losses. Evacuation ends.
3.6. near Paris 3 French fighters shot down to 1 loss (pilot captured, released after France surrendered)
6.6 Adolf Galland takes over III/JG26 and starts his organizational renovations...
8.6. II/JG26's 7./JG26 against Hurricanes near Paris again, Klaus Mietusch shot down, crash landed, had his butt shot through by a French civilian but he escaped and made it
9.6. free hunt over Paris, Bürschgens' victory which he writes about in great detail. One Bf 109 damaged.
Transfer to Villacoublay, war ended soon and the regiment didn't manage to find action any more.
During Dutch, Belgium and French campaign, air-to-air losses(does not include landing accidents and such) were: 92-19 plus the regiment lost one fighter to anti-aircraft fire.
160 claims, 100 confirmed/granted victories to 20 losses in air. Theres some bombers and Defiants there, but majority of the victories(most of the ones against RAF and early fights against the French are cross-checked) were definitely not against recon planes and antiquated bombers.
That also means that some pilots were lost as KIA outside of combat too, those 2 at least.
Edit: I can add details of at least Galland's victories in these too, as he happened to be in III/JG26. If needed.