A method of modifying a turbine blade (100, 100') in an initial form, the turbine blade (100, 100') in the initial form including a root defining a plurality of supply channels configured to receive a supply of pressurized gas, a blade tip, and an airfoil extending in a radially outward direction from the root to the blade tip, the airfoil having a pressure side surface and a suction side surface connected to the pressure side surface of the airfoil by a leading edge of the airfoil and a trailing edge of the airfoil, the trailing edge of the airfoil defining a trailing edge cooling aperture, wherein the turbine blade (100, 100') defines a first serpentine interior cooling passage having a first leg, a second leg, a third leg, a first junction portion, and a second junction portion, the first leg configured to receive the pressurized gas from at least one supply channel of the plurality of supply channels, the first leg extending radially within the airfoil and connected to the second leg by the first junction portion proximate the blade tip, the second leg extending radially between the first junction portion and the second junction portion, the second junction portion connecting the second leg to the third leg, the third leg extending radially from the second junction portion toward the blade tip and connected to the trailing edge cooling aperture to exhaust the pressurized gas to an exterior of the turbine blade (100, 100'), the blade tip defining a plurality of tip cooling apertures through a pressure side surface of the blade tip at a location along the blade tip that overlaps in an axial direction with the third leg, the method comprising removing a section of the turbine blade (100, 100') that includes a plurality of the tip cooling apertures through the pressure side surface of the blade tip, attaching a turbine blade (100, 100') replacement section in place of the removed section of the turbine blade (100, 100') to form a modified turbine blade (100, 100'), the turbine blade (100, 100') replacement section defining a plurality of replacement tip cooling apertures that are disposed radially outward of the third leg and overlap in the axial direction with the third leg, wherein the plurality of replacement tip cooling apertures includes at least one forward tip cooling aperture and at least one aftward tip cooling aperture, characterized in that the turbine blade (100, 100') replacement section is configured to supply a first portion of the pressurized gas from the first junction portion directly to the at least one forward tip cooling aperture and to supply a second portion of the pressurized gas from the third leg directly to the at least one aftward tip cooling aperture. removing a section of the turbine blade (100, 100') that includes a plurality of the tip cooling apertures through the pressure side surface of the blade tip, attaching a turbine blade (100, 100') replacement section in place of the removed section of the turbine blade (100, 100') to form a modified turbine blade (100, 100'), the turbine blade (100, 100') replacement section defining a plurality of replacement tip cooling apertures that are disposed radially outward of the third leg and overlap in the axial direction with the third leg, wherein the plurality of replacement tip cooling apertures includes at least one forward tip cooling aperture and at least one aftward tip cooling aperture, characterized in that the turbine blade (100, 100') replacement section is configured to supply a first portion of the pressurized gas from the first junction portion directly to the at least one forward tip cooling aperture and to supply a second portion of the pressurized gas from the third leg directly to the at least one aftward tip cooling aperture.