Frame rates at large airports have always been lower because there are a lot more objects that need to be rendered. Also, there are 3rd party developer objects and scenery that may not have been optimized yet.
Also, are you using the same graphics settings from SU9 or SU8? I discovered that my SU9 settings made my FPS and graphics worse with SU10. There isn’t any automatic update of settings with the SU10 installation.
FWIW with SU10, I am seeing outside of large airports 50 to 60 FPS. In and around large airports I’m seeing 30 to 40 FPS, acceptable for me. Prior to SU10, large airports were about 25 to 35 FPS.
In the past, there were problems with the scenery in and aroun KATL dropping FPS to about 5 - 15 FPS, clearly unacceptable.