Airspeed
Speed of an aircraft relative to the surrounding air
In aviation, airspeed is the speed of an aircraft relative to the air it is flying through. In contrast, the ground speed is the speed of an aircraft with respect to the surface of the Earth. It is difficult to measure the exact airspeed of the aircraft, but other measures of airspeed, such as indicated airspeed and Mach number give useful information about the capabilities and limitations of airplane performance. The common measures of airspeed are:Indicated airspeed (IAS), what is read on an airspeed gauge connected to a pitot-static system.
Calibrated airspeed (CAS), indicated airspeed adjusted for pitot system position and installation error.
True airspeed (TAS) is the actual speed the airplane is moving through the air. When combined with aircraft direction, wind speed and direction, it can be used to calculate ground speed and direction.
Equivalent airspeed (EAS) is true airspeed times root density ratio. It is a useful way of calculating aerodynamic loads and airplane performance at low speeds when the flow can be considered incompressible.
Mach number is a measure of how fast the airplane is flying relative to the speed of sound.
“Airspeed” enters the record as speed of an aircraft relative to the surrounding air. Crown Archives preserves that source wording while asking what Airspeed, Speed and aircraft can confirm, complicate or overturn.
Why this record matters
“Airspeed” is worth following because a concise public description often conceals a longer documentary argument. Here, Airspeed, Speed and aircraft provides the most credible route into that argument.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Jul 16, 2026.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
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This entry incorporates text from “Airspeed” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.