Abstract: An air turning vane and rail assembly for promoting laminar air flow in angled duct work transition sections includes longitudinally spaced apart air turning vanes transversely disposed between a pair of flat rails. Each turning vane is a hollow double-plate airfoil having a convex front airfoil plate, and a concave rear airfoil plate joined at their edges. Each rail has a plurality of longitudinally spaced apart, upstanding tabs each having an upper trapezoidally-shaped portion and a lower rectangularly-shaped pedestal portion. Each tab has a pair of laterally opposed, outwardly and downwardly angled edge walls, each joined at its lower end to a vertically disposed pedestal edge wall. The width of the pedestal is greater than the maximum lateral spacing between the front and rear airfoil plates.