Hi,
I installed this game, but wasn't able to play it : the FPS are so low in most of the situation that's the game is unplayable.
In fact, the only situation where the game is smooth is when flying, with only open & clear sky toward.
When in 3D virtual cockpit, external view, seing other plane/object or just the ground, the game runs in slideshow mode.
What cause this ?
I've tried most of the graphical options, didn't help.

I have the same issue, have you came to a solution?
I'm running the game with a C2D 4500 2.0, GeForce 8500 GT, 2Gb RAM

Are you running on a multi-core system? e.g. a Core-2-Duo or I7?

Yeah, is that the problem ?

Easy way to find out, just run the game then ctrl-alt-del and bring up the task manager. Go to the process tab and find the process for the game, right click it and set the core affinity to run on core0. Close the task manager and see if the game runs better.

It may be the problem. Multi-core systems (especially ones with hyperthreading) tend to handle the threading for programs designed on/for single core systems oddly. Try what the above poster suggests, and turn off affinity for extra cores. Often when an old game runs oddly slowly or too fast, that's the problem. There are a few programs out there you can use to have it automatically use only one core, but I won't make any recommendations. Try searching google for one.

I'll try it and be back to you. Is there a way to automatically set it just for the game ?

Has anyone found a solution? I really want to fly this sim, but can't because of the choppy frame rates.
I tried messing with affinity settings, but no dice.
C2D, 8800 GTX, 2GB Ram

I'm getting the same. Windows XP, Core 2 Duo E8400 (3GHz), nVIDIA 9600GT, 4GB installed RAM (3GB visible). It only really becomes unplayable around the carrier, but that's enough to make the whole game unplayable.
It was set with affinity to just a single core by default. Changing this didn't seem to make a difference.