An airfoil (10) for a gas turbine engine in which the airfoil (10) includes an internal cooling system (14) with one or more internal cavities having an insert (18) contained within an aft cooling cavity (76) to form nearwall cooling channels having enhanced flow patterns is disclosed. The flow of cooling fluids in the nearwall cooling channels may be controlled via a plurality of cooling fluid flow controllers (22) extending from the outer wall (24) forming the generally hollow elongated airfoil (26). The cooling fluid flow controllers (22) may be collected into spanwise extending rows. In at least one embodiment, the cooling fluid flow controllers (22) may be positioned within a pressure side nearwall cooling channel (48) and a suction side nearwall cooling channel (50) that are both in fluid communication with a trailing edge channel (30). The trailing edge channel (30) may also include cooling fluid flow controllers (22) extending between the outer walls (12, 13) forming the pressure and suction sides.