What term describes the speed of the aircraft over the ground?

Groundspeed refers to the actual speed of the aircraft relative to the ground. It takes into account the effects of wind, which can either increase or decrease the aircraft's speed over the ground compared to its speed through the air. Groundspeed is crucial for navigation and time estimations during flight, as it directly affects how quickly an aircraft reaches its destination.

The other terms listed serve different purposes in aviation. Heading speed is not a standard term used for measuring speed, but rather refers to the direction an aircraft is pointing. Airspeed indicates how fast the aircraft is moving through the air and does not consider ground effects, while indicated speed is the airspeed read directly from the aircraft's instruments, corrected for instrument errors but still not accounting for wind. By focusing on groundspeed, pilots can make more accurate calculations regarding their flight path and time to destination.