What kind of wind can unexpectedly shift direction, posing hazards during critical phases of flight?

Variable wind is characterized by changes in direction and speed, which can occur suddenly and without much warning. This unpredictability can create significant challenges for pilots, particularly during critical phases of flight such as takeoff and landing. In these moments, consistent wind direction is crucial for maintaining control and ensuring safety. When winds shift unexpectedly, they can affect maneuverability and require rapid adjustments by the pilots, increasing the risk of an accident.

Gusty wind, while also a potential hazard, typically refers to variations in wind speed rather than direction. Tailwinds can aid in takeoff and landing but do not imply shifting direction. Steady wind is ideal for flight operations as it provides a consistent flow for pilot navigation and control. Thus, the unique characteristic of variable wind makes it particularly hazardous compared to the other types listed.