Check out Mike's Mods page you can get the JSGME there,
https://thatoneplease.co/indexWOFFWOTR.htmlGo to WOFF section and go to "tools" it's there at the top.
There's a lot of aircraft in the air in campaign. Set Regional Air Activity in Workshop ("more settings" page) it to "Light " or "Very light". Turn off forced encounters.
If you don't see many aircraft they are there, turn on labels and switch onto "activity" to see many you will miss. If in early war yours it is correct you will see few. In later 1916 onwards you will a see a lot more (and have worse FPS of course) - it also depends greatly on WHERE you are. There are 4 regions - Alsace is very quiet compared to Flanders say. Choose another.