Tan when gliding when looking for max range one looks for an optimum IAS (Indicated Airspeed). But in actual fact a better number is the angle of attack to maximize the CL to CD (Coefficient of Lift to Drag) to approximately 17 with flaps and slats in.
In training they emphasize IAS, especially in small planes, but I was wondering if the angle of attack was used instead for max glide range.