My suggestion is to try and determine if there’s a specific part of the airport that seems worse than other parts. Get in the drone camera, enable some sort of fps counter and pan around to see if you can pinpoint a direction that drops fps more than others.
It could be many things such as very large textures being used, a building modeled with way too many sides/vertices, parked static aircraft, or it could be something else entirely that has nothing to do with the specific add-on.
Definitely remove everything from your community folder except the add-on in question and see if you have the same result.
Also, post your system specs including CPU, ram and your GPU specs including amount of VRAM. VRAM is extremely important when it comes to troubleshooting scenery add-ons.