The disclosed composite airfoil includes a three-dimensional composite core extending longitudinally and having a chord-wise direction. The core has a core in-plane thickness extending between opposing sides in a through-plane direction generally perpendicular to the chord-wise and longitudinal directions. A composite skin covers the opposing sides and has an exterior surface providing an airfoil contour. The skin includes a total skin in-plane thickness corresponding to a sum of thicknesses through the skin in the through-plane direction from each of the opposing sides to their adjoining exterior surface. A sum of the core in-plane and total skin in-plane thicknesses at a central portion of the composite airfoil is a total in-plane thickness. The total skin in-plane thickness at the central portion is less than 50% of the total in-plane thickness.