GTX 980ti
I5 4670k overclocked

The texture resolution doesn't make a difference unfortunately. I do use a 4K monitor but the performance is the same as before when I used a 1920 x 1080 monitor.

Thanks for the quick reply! I removed all the terminal BGL's and now the fps (when looking at the terminal area) has increased to about 22fps on average. When looking at Boston city itself the fps is still in excess of 30fps. Not sure what my setup particularly dislikes about the terminal buildings?...

I've been looking through this forum trying to find an answer to this problem; I have almost exactly the same computer specs as above, yet Boston is the one airport I have that performs with 10fps, noticeably this bad when looking at the terminal itself. I don't think dynamic lighting is the problem...