Abstract: A method is provided for making a two-piece hollow airfoil having a complex geometry. Two metal sheets are formed into initial shapes so as to have a mean camber and twist. A series of raised ribs is machined onto the external side of each of the two sheets. The two sheets are joined together and sealed to form an in-process assembly. The assembly is subjected to high temperature and pressure to diffusion bond the sheets together at selected points. The assembly then subjected to internal pressure at high temperature in order to inflate and superplastically deform the assembly to the desired shape. Excess material is machined off after the inflation step.