An airfoil (400; 500; 600; 700) for a gas turbine engine, the airfoil comprising: an airfoil body (402; 502; 602; 702) extending between a leading edge (404; 504; 604; 704) and a trailing edge in an axial direction and between a pressure side and a suction side in a circumferential direction; an internal cold wall (414; 714) defining a leading edge feed cavity (416; 516; 616; 716) proximate the leading edge of the airfoil body; an external hot wall (412; 712) defining a leading edge skin core cavity (410; 510; 610; 710) between the external hot wall and the internal cold wall, wherein the leading edge skin core cavity comprises an impingement inlet portion (420; 520A, 520B; 620A, 620B; 720) and a film outlet portion (422; 522A, 522B; 622A, 622B; 722); at least one impingement hole (418; 518A, 518B; 618A, 618B; 718) formed in the internal cold wall and fluidly connecting the leading edge feed cavity to the impingement inlet portion; and at least one film cooling hole formed in the external hot wall and fluidly connecting the film outlet portion to an exterior of the airfoil body, characterised in that the impingement inlet portion has a first height (H 1) defined as a distance between the external hot wall and the internal cold wall for a length of the impingement inlet portion, and the film outlet portion has a second height (H 2) that is greater than the first height; and a leading edge rib (526; 626) extends between the external hot wall and the internal cold wall and divides the leading edge skin core cavity (510; 610), wherein the leading edge rib fluidly separates the leading edge skin core cavity to define a first impingement inlet portion (520A; 620A) and a second impingement inlet portion (520B; 620B). an airfoil body (402; 502; 602; 702) extending between a leading edge (404; 504; 604; 704) and a trailing edge in an axial direction and between a pressure side and a suction side in a circumferential direction; an internal cold wall (414; 714) defining a leading edge feed cavity (416; 516; 616; 716) proximate the leading edge of the airfoil body; an external hot wall (412; 712) defining a leading edge skin core cavity (410; 510; 610; 710) between the external hot wall and the internal cold wall, wherein the leading edge skin core cavity comprises an impingement inlet portion (420; 520A, 520B; 620A, 620B; 720) and a film outlet portion (422; 522A, 522B; 622A, 622B; 722); at least one impingement hole (418; 518A, 518B; 618A, 618B; 718) formed in the internal cold wall and fluidly connecting the leading edge feed cavity to the impingement inlet portion; and at least one film cooling hole formed in the external hot wall and fluidly connecting the film outlet portion to an exterior of the airfoil body, characterised in that the impingement inlet portion has a first height (H 1) defined as a distance between the external hot wall and the internal cold wall for a length of the impingement inlet portion, and the film outlet portion has a second height (H 2) that is greater than the first height; and a leading edge rib (526; 626) extends between the external hot wall and the internal cold wall and divides the leading edge skin core cavity (510; 610), wherein the leading edge rib fluidly separates the leading edge skin core cavity to define a first impingement inlet portion (520A; 620A) and a second impingement inlet portion (520B; 620B).