What does the yellow arc in an aircraft's airspeed indicator represent?

The yellow arc on an aircraft's airspeed indicator indicates the caution range for flight. This range signifies speeds that should be approached with caution. It typically lies between the lower limit of the green arc, which is the normal operating range, and the upper limit of the red radial line, which indicates the never-exceed speed.

Flying within this yellow arc suggests that the pilot should be vigilant about performance and handling characteristics, as operating within these speeds can lead to undesirable flight conditions or increased risk of stalling depending on the aircraft's configuration and flying conditions. It serves as a warning that while these speeds are technically flyable, they should be avoided unless necessary, and pilots should exercise care when operating in this range to maintain safety.