Calibrated Airspeed (CAS) is the speed of an aircraft corrected for instrument and position errors. It is measured in knots and provides pilots with a more accurate representation of the aircraft's performance compared to indicated airspeed, which can be affected by factors like air density and instrument inaccuracies. CAS is essential for safe flight operations, as it helps pilots determine stall speeds and maneuvering capabilities. By using CAS, pilots can ensure they are flying within the aircraft's performance limits, which is crucial for maintaining safety during various phases of flight, such as takeoff and landing.