Airspeed indicator markings

Example values: Cessna 172S, knots indicated airspeed (KIAS)

AIRSPEED knots
White arc: 40–85 ktFlap operating range. Bottom = VSO (stall, landing config). Top = VFE (max flaps extended).
Green arc: 48–129 ktNormal operating range. Bottom = VS1 (stall, clean). Top = VNO (max structural cruising).
Yellow arc: 129–163 ktCaution range. Smooth air only.
Red line: 163 ktVNE, never exceed speed.
100 kt

Not marked on the ASI: VA (maneuvering speed varies with weight — see the POH). Always use the POH/AFM values for the aircraft you fly.