The plural of airspeed; the speed of an aircraft relative to the air around it, not the ground.
From 'air' plus 'speed' (Old English spēd, from Proto-Germanic *spōdi- meaning 'prosperity, success'). The term became standard in aviation vocabulary in the early 1900s to distinguish from ground speed.
A plane flying at 500 mph airspeed could be going 400 mph over the ground if there's a headwind, or 600 mph if there's a tailwind—pilots care about airspeed because that's what determines how much lift the wings generate.
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