An airfoil for a turbine of a gas turbine engine is provided comprising an outer wall structure defining at least one inner cavity adapted to receive a cooling fluid. The wall structure comprises at least one cooling fluid path circuit communicating with the at least one inner cavity. The cooling fluid path circuit comprises: at least one metering opening extending from an inner surface of the wall structure such that the metering opening communicates with the at least one inner cavity; at least one intermediate diffusion region communicating with the metering opening; an intermediate metering opening positioned downstream from the intermediate diffusion region and communicating with the intermediate diffusion region; and, an end diffusion region positioned downstream from the intermediate metering opening for communicating with the intermediate metering opening and extending to an exit in an outer surface of the wall structure.