What happens to aircraft performance as the wind turns perpendicular to the runway?

When the wind turns perpendicular to the runway, the impact on aircraft performance primarily affects the pilot's ability to maintain directional control. In this scenario, the crosswind can exert a substantial force on the aircraft, which complicates the takeoff and landing phases.

As the aircraft moves down the runway, the crosswind will push the fuselage away from the centerline. Consequently, the pilot must apply corrective inputs, such as using ailerons to counteract the wind's force and maintain proper alignment with the runway. This need for constant adjustments makes directional control more challenging, particularly at lower speeds during takeoff and landing when the aircraft is most vulnerable to wind gusts.

Therefore, this situation highlights that the aircraft’s performance in terms of directional control is negatively affected, as the pilot has to work harder to keep the aircraft on the intended flight path. The option indicating that directional control becomes increasingly difficult accurately reflects the challenges posed by a perpendicular wind.