When planning a route, which speed should you use to determine ground speed?

When planning a route, the appropriate speed to utilize for determining ground speed is True Airspeed (KTAS). This measurement represents the actual speed of the aircraft relative to the surrounding air mass.

Using KTAS is crucial because ground speed may vary due to wind conditions. While Airspeed (KIAS) measures the speed of the aircraft through the air, it does not account for how wind affects the aircraft's progress over the ground. By taking the true airspeed into account and incorporating wind effects, you can calculate your ground speed, thus ensuring a more accurate understanding of your travel time and route planning.

The other measurements, such as KIAS (Indicated Airspeed), primarily reflect the aircraft's airspeed without correcting for altitude and ambient temperature, making it less effective for ground speed determination. Knots Ground Speed does measure the speed over the ground but is often derived from reliable true airspeed data adjusted for winds rather than being a speed that can be directly used in route planning. Miles Air Speed is not a standard aviation term and does not provide relevant information for ground speed calculations.