The l1011 -500 wing was different on the UK reg jets compared to the rest. To meet uk g loading requirements 20 vortex generators were added to the upper surface of each wing. I've flown both types and the only difference noticable is a very very small increase in fuel burn. . .Other devices include "t" shape trailing edges and chouchelmin (sp) carrots. They are all used to fix flow seperation problems at various flight configs. You cannot build a wing that does everything perfectly there is always a compromise.. .Flaps and slats are the most obvious examples of this.