Abstract: The wall of a hollow airfoil has a longitudinally extending slot in its external surface which is intersected, at its base, by a plurality of coolant passages in a longitudinally extending row. Each coolant passage has a metering portion at its inner end which communicates with a coolant compartment within the hollow airfoil. Each passage includes a pair of walls downstream of the metering portion which diverge from each other in the longitudinal direction and intersect with the base of the slot to form an outlet for the passage. The diverging walls of adjacent passages substantially meet each other at the base of the slot, wherein coolant fluid from the metering portions of the passages diffuses in the longitudinal direction as it flows toward and into the slot, filling the entire slot and forming a thin, continuous film of coolant downstream of and along the entire length of the slot over the external surface of the airfoil.