What does the white color marking on the airspeed indicator denote?

The white color marking on the airspeed indicator indicates the flap operating range. This range shows the speed limits at which the aircraft’s flaps can safely be extended. When pilots extend flaps for landing or takeoff, it is crucial they remain within this speed range to ensure safe and effective flap operation, as exceeding these limits can lead to potential aerodynamic issues or stall risk. Understanding the flap operating range is vital for safe aircraft handling, particularly during critical phases of flight such as approach and landing.