What is the maximum airspeed indicated by the red line?

The maximum airspeed indicated by the red line on the airspeed indicator represents the never exceed speed (V_ne) for the aircraft. This limits the speed at which the airplane should not exceed during flight to ensure structural integrity and safety of operation.

For the Cessna 152, this value is indeed 149 knots indicated airspeed (KIAS). Exceeding this speed can lead to significant structural stress and potential failure of the airframe.

The other airspeeds listed do not represent the never exceed speed for the Cessna 152 and are typically associated with other flight parameters, such as stall speeds, maneuvering speeds, or cruise speeds specific to different aircraft configurations. It’s important for a pilot to adhere to these limitations as part of safe flying practices, emphasizing the significance of understanding and respecting the aircraft's limitations as defined by the manufacturer.