A gas turbine airfoil having internal cooling passages is formed by additive manufacturing. Layers of superalloy powder are fused by an energy beam using a two-dimensional pattern providing unmelted areas forming passageways therein. Layers of the powder are added and fused using sufficient two-dimensional patterns to form the entire airfoil with the desired pattern of internal cooling passages. After completion of the formation of the airfoil, it may be hot isostatic pressed, directionally recrystallized, bond coated, and covered with a thermal barrier layer.