Flight Simulator X has not even been officially released in the USA, and we already have a handful of people complaining about its performance. It's become pretty much clear that you need recent hardware to run FSX decently, but even people with high-end systems are having trouble finding optimal settings for it. The major performance hit comes with the new autogen trees and buildings, which can completely ruin your flight experience over big cities if not configured properly. This guide's objective is to provide some tweaks for you to optimize the simulator performance.

Check it out:  Flight Simulator X - Performance Tweaks