After commenting the inventory was getting a little one sided for the Allies, I did an actual count and it turns out I was wrong.
After adding the Euler 2D and DR 1 there are 36 aircraft on both sides. What threw me off was there are more skins on the Allied side. Meaning there are both British and French skins for many of the Nieuports, Spads and Sopwiths.
BTW, the Euler 2D was a direct copy of the Nieuport 11. Thirty were built but the combat record is sketchy on whether they saw combat. There was a 1D but the performance was so poor it never saw production so I decided to leave that one out. I could put it in if we don't have enough 1914-1915 planes.
The Euler DR1 was a prototype triplane version of the same plane but with an upgraded 160HP rotary. Only one was built in late 1917. I added it under the "what-if" rule.
Just for the hell of it I started searching for any other planes that inspired crossovers by the opponents. Haven't found any others yet but if anyone knows of some let me know.