For what purpose is indicated airspeed primarily used?

Indicated airspeed is primarily used to communicate the speed of an aircraft relative to the surrounding air. It is crucial for ensuring that air traffic controllers have accurate information about an aircraft's speed for maintaining safe separation between aircraft and for sequencing arrivals and departures at airports. The indicated airspeed allows both pilots and controllers to understand the aircraft's performance characteristics and operational capabilities, which plays a significant role in managing air traffic and ensuring safety.

While climbing efficiency, descent planning, and weather assessment are important aspects of flight operations, they do not directly relate to the primary use of indicated airspeed in air traffic operations. Indicated airspeed is a critical parameter for communication, enabling effective coordination and safety between pilots and air traffic control.