Table of Contents
What Is Ground Speed?
Ground speed is the aircraft's speed relative to the ground surface. It differs from airspeed due to wind effects. A headwind reduces ground speed while a tailwind increases it. Ground speed determines actual travel time and fuel consumption for a given distance.
Pilots must calculate ground speed for flight planning, fuel calculations, and estimated time of arrival. Air traffic control uses ground speed to maintain separation between aircraft. The difference between true airspeed and ground speed is entirely due to the wind vector.
Ground Speed Formula
Speed Conversion Table
| Knots | km/h | mph |
|---|---|---|
| 100 | 185.2 | 115.1 |
| 200 | 370.4 | 230.2 |
| 300 | 555.6 | 345.2 |
| 500 | 926.0 | 575.4 |
Frequently Asked Questions
Why do flights take longer in one direction?
The jet stream, a high-altitude wind band flowing west to east at 100-200 knots, creates significant headwinds for westbound flights and tailwinds for eastbound flights. A flight from New York to London might take 7 hours, while the return takes 8 hours due to prevailing headwinds.
What is the difference between TAS, IAS, and GS?
Indicated Airspeed (IAS) is what the cockpit instrument reads. True Airspeed (TAS) corrects IAS for altitude and temperature. Ground Speed (GS) is TAS adjusted for wind. At high altitudes, TAS can be much higher than IAS due to thinner air, while GS can differ significantly from TAS due to winds.