What does airspeed mean?
Airspeed is the speed at which an aircraft moves through the air around it, as opposed to its speed over the ground. Measured in knots by a pitot-static system and displayed on the airspeed indicator, it is one of the most critical readings in the cockpit: stall speeds, flap limitations, and structural limits are all defined in terms of airspeed rather than groundspeed. Because wind shifts the relationship between the two, an aircraft facing a strong headwind may show high airspeed while barely progressing across the landscape, while a tailwind produces the opposite effect. Aviators distinguish several variants — indicated, calibrated, equivalent, and true airspeed — each accounting for instrument error or atmospheric conditions such as altitude and temperature. Though primarily a term of aviation and aerodynamics, airspeed also applies to any object's motion relative to the air, from birds to projectiles.
nounThe speed of an aircraft relative to the air through which it is moving, as distinct from its speed relative to the ground. It is typically measured in knots by instruments such as the pitot-static system.
- The speed of an aircraft relative to the surrounding air mass, measured by instruments such as the airspeed indicator.
- More broadly, the speed of any object relative to the air through which it moves (e.g. a projectile or bird).
"The pilot reduced the airspeed before extending the landing flaps."
"The pilot eased back on the throttle as the airspeed climbed past the recommended cruise setting."
"Strong headwinds meant the aircraft's groundspeed was far lower than its airspeed for the entire crossing."
Rarely pluralised; usually treated as a single measurable quantity per aircraft or condition.
"The manual lists the aircraft's key airspeeds for takeoff, climb, and landing."
A plane parked on the runway with a strong headwind can have real airspeed without moving an inch — which is why wind tunnels work and why pilots trust airspeed over groundspeed when it matters most.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of airspeed
Airspeed is a straightforward English compound of 'air' and 'speed', both of ancient pedigree: 'air' derives from Latin 'aer' via Greek 'aēr', while 'speed' comes from Old English 'spēd'. The compound arose in the early twentieth century alongside powered flight, when aviation demanded precise terminology for motion through the atmosphere. It shares its 'air' element with other flight-era coinages such as 'aircraft' and 'airline'.
How airspeed is actually used
A technical term used chiefly in aviation and aerodynamics; in everyday speech it appears mainly in news reports about flying. Pilots distinguish several variants — indicated airspeed (IAS), true airspeed (TAS), calibrated airspeed (CAS), and equivalent airspeed (EAS) — each correcting for different instrument and atmospheric effects.
Easily confused with airspeed
Airspeed measures an aircraft's speed relative to the surrounding air, while groundspeed measures its speed relative to the ground, the two differing because of wind.