Definition
The speed of an aircraft relative to the air mass through which it is moving. Airspeed is distinct from groundspeed and is the speed that matters aerodynamically — it determines lift, drag, and how the aircraft handles. Several specific forms are recognized: Indicated Airspeed (IAS), the speed shown directly on the airspeed indicator; Calibrated Airspeed (CAS), IAS corrected for instrument and position errors; Equivalent Airspeed (EAS), CAS corrected for compressibility at higher speeds and altitudes; and True Airspeed (TAS), EAS corrected for air density, representing the actual speed of the aircraft through the surrounding air mass.
Plain English
How fast the aircraft is moving through the air around it — not how fast it is moving over the ground. The wings only know about airspeed; that is what keeps the aircraft flying.
Context Anchor
Pilots see airspeed on the airspeed indicator and use it during takeoff, climb, cruise, approach, and landing.
Derivation
Combines 'air' (the atmosphere as the reference medium) with 'speed' (rate of motion) to distinguish motion through the air from motion measured over the ground.
Why Pilots Care
Airspeed governs lift production, stall margins, and structural limits, directly affecting safety and performance.
Grounding Statement
With a strong headwind, an airplane can have plenty of airspeed even while moving slowly over the ground.
Intuition Check
Do not assume airspeed means speed across the ground. Airspeed is through the air; speed across the earth is a different measurement.
Example Sentence 1
On final approach, the pilot held the airspeed steady at 65 knots to ensure a stable touchdown.
Example Sentence 2
A headwind reduced ground speed but left the required airspeed for takeoff unchanged.