This site is being deprecated.
Please see the official X‑Plane Support page for help.
The cockpit of the plane might be super detailed and require more computer power than the world scenery does. I see this with the airliners most often. The best you can do is follow these instructions for setting the rendering options. Make sure you base it on the most intensive plane, scenery, weather, etc you want to use. That means if using light scenery areas or clear weather you may have a really high frame rate, but you won't have to adjust it every time you want to use a powerful plane or a lot of clouds.
This site is no longer being actively maintained.