Ekranoplans or Ground Effect Vehicles (GEV) fly low enough to the ground that their wings stay in the ground effect. This increases lift and efficiency.
But GEV fly in the lower atmosphere (literally ground level) which greatly increases drag compared to flying in the stratosphere.
Is it possible that a GEV designed using contemporary composite materials and high bypass engines could be more efficient per cargo weight-mile (or passenger mile) than a tradition airliner? Or are GEV inherently less efficient due to the altitude they fly at?
This question is specific to fuel efficiency over distance. Feasibility, safety, navigation, time, and cost of airframe are not part of the equation.