Gas turbine engine (GTE) airfoils, such as rotor and turbofan blades, having multimodal thickness distributions include an airfoil tip, and an airfoil root opposite the airfoil tip in a spanwise direction. The GTE airfoil has a first, second and third locally-thickened region, with the first locally-thickened region defined at the airfoil root. A maximum thickness of each chord between the airfoil root and the airfoil tip transitions toward the leading edge between the first locally-thickened region and the second locally-thickened region, and the third locally-thickened region extends in the spanwise direction. A chord line that extends through the third locally-thickened region contains a first local thickness maxima and a second local thickness maxima interspersed with at least two local thickness minima, and the first local thickness maxima is defined by the third locally-thickened region and is greater than the second local thickness maxima.