Throw out that CPU likely your issue I have an i5 8400 rtx2060super and get fps drops at those airports at least in the 20s as shown in the screenshot. Smaller airports you should be getting a lot more than 40fps with that GPU. Get a 9900k hopefully you have a good Z390 board.
My i5 8400 is in a few% slower than your 9400 but that 160$ cpu is not a good pair with a 1500$ gpu Mine is back and forth limited by mainthread and GPU.
