Which of the following factors is NOT part of determining airspeed?

The factor that is not part of determining airspeed is aircraft weight. Airspeed refers to the speed of an aircraft relative to the surrounding air and is influenced by various factors such as wind direction, altitude, and aircraft design.

Wind direction affects how an aircraft acts against or with the wind, which can impact the ground speed versus airspeed. Altitude can change air density, which impacts lift and performance, thus influencing the required airspeed for effective flying. Aircraft design, including shape and propulsion system, is crucial for how efficiently an aircraft moves through the air.

Aircraft weight, while significant for takeoff, landing performance, and overall flight dynamics, does not directly influence the measurement of airspeed itself. Airspeed is typically gauged with respect to the aircraft's interaction with the air it flies through, rather than its mass. Therefore, in this context, aircraft weight is the correct answer for being unrelated to the determination of airspeed.