Final answer:
It is false that wands must always be used when marshaling in a plane; use depends on airport regulations and visibility conditions.
Step-by-step explanation:
Whether it is true or false that one must always use wands when marshaling in a plane depends on the specific airport regulations and standard operating procedures for ground crew. However, it is commonly expected for ground personnel, known as marshals, to use illuminated wands during low-visibility conditions such as nighttime or inclement weather to ensure clear communication with the pilots. During daylight and clear conditions, marshals may use hand signals without wands, though wands can enhance the visibility of signals.