What is true airspeed (TAS)?

True airspeed (TAS) represents the actual speed of the aircraft through the air. It's a crucial measurement for pilots because it accounts for changes in air density that occur at different altitudes and temperatures. While calibrated airspeed (CAS) is corrected for instrument and installation errors, TAS goes a step further by factoring in the effects of altitude and air temperature on the actual density of the air.

As altitude increases, the air density decreases, which affects the aircraft's performance. Therefore, to accurately determine true airspeed, pilots must adjust their calibrated airspeed for these factors. This makes TAS especially important for navigation and performance calculations during flight. It helps in ensuring that the aircraft operates efficiently and within its performance limits, particularly at higher altitudes where adjustments due to changes in air density become significant.

Other options address related concepts, such as speed relative to the ground or wind corrections, but they do not define true airspeed accurately. The understandings of calibrated airspeed and wind corrections may be components of flight planning and operational strategies, yet they do not encompass the comprehensive definition of TAS that reflects an aircraft's actual performance in the atmosphere.