CloD is the most fantastic combat flight sim but it seems that the landscape rendering is causing the major fps/stuttering problems. Wings of Prey is not actually comparable but inferior to Clod in most aspects especially gameplay, aircraft modelling, mission building and lack of any editable land objects but I must admit that the landscape looks much more realistic and has smooth rendering during game play. I wonder why the Maddox team did not use similar algorithms for their mapping coding, but I think there should have been good reasons for this decision.
http://vimeo.com/14661191