Definition
The speed of an aircraft relative to the surface of the earth. It is the airspeed adjusted for the effect of wind, and represents how fast the aircraft is actually moving over the ground.
Plain English
How fast the aircraft is travelling over the ground below it. A headwind makes ground speed slower than airspeed; a tailwind makes it faster.
Context Anchor
Seen in navigation, flight planning, cockpit displays, and estimates of time to the next airport or checkpoint.
Why Pilots Care
It determines actual time en route, fuel burn, and whether arrival expectations will be met regardless of indicated or true airspeed.
Intuition Check
Do not assume ground speed is the same as airspeed. Ground speed is your progress over the ground; airspeed is how fast the airplane is moving through the air around it.
Example Sentence 1
With a 20-knot tailwind, the aircraft's ground speed was 140 knots even though its airspeed was only 120.
Example Sentence 2
The GPS showed a ground speed of only 95 knots while flying into the headwind, lengthening our time to the destination.