Motion Pictures run at 33 fps. So anything over that would look smooth on a screen. If you're below that, you may notice that performance is hindered... The images or aircraft will kinda look like it's moving in slow moiton, but it's really not, it just skips a frame here and there.

To increase the frame rate in RF you can easily remove items from the screen or lower that 3d intensity... I think if you go to airport, then select visible items. You can uncheck the things you want removed... You can remove runways, trees, spectators, other planes, benches, silos, hay bales, rocks, grass, gravel, etc.... This should bring up the frame rate...

If that doesn't work, go to the video graphics settings page and set the settings to a lower value... If you're on high, try medium.. If on medium go to low... etc. etc. etc.

I'm currently running 800mhz, w 256megs or RAM and an old 32meg NIVIDIA Graphics Card and my frame rate never goes below 40fps... Very smooth... As I fly away from myself, it goes upto 145fps...