What does the symbol "/" signify in air traffic control terminology?

In air traffic control terminology, the symbol "/" signifies "until." This usage helps to provide clear instructions regarding time or conditions that remain in effect. For example, a controller might use this symbol when specifying a route or altitude to maintain "until" another point or instruction is given. By using "/" to convey "until," it minimizes the potential for misunderstanding and enhances the clarity of communications in an environment where precision is critical.

The other options, while they might denote familiar concepts in various forms of communication, don't accurately reflect the meaning of the symbol in the context of air traffic control. "End of communication," "in addition to," and "start of a new instruction" imply distinct meanings that do not align with the established usage of "/" in this specific field.