What type of wind is NOT parallel to the runway?

The type of wind that is not parallel to the runway is a crosswind. A crosswind blows across the runway, impacting the lateral position of the aircraft during takeoff and landing. This wind direction presents challenges for pilots as it can cause the aircraft to drift off the centerline of the runway, requiring them to make adjustments to maintain control.

In contrast, a tailwind and a headwind are both parallel to the runway. A tailwind blows in the same direction as the aircraft's movement, increasing ground speed during takeoff but potentially complicating landing. A headwind blows directly against the aircraft's movement, which can enhance lift and reduce ground speed needed for landing and taking off. Variable wind, while it describes changing wind directions and speeds, can still include periods of wind that are parallel to the runway. Therefore, crosswind stands out as the wind type that is distinctly not parallel to the runway.