What phraseology is used to assign a higher altitude to an aircraft?

Using the phraseology "Climb and maintain (altitude)" is the standard and clear way to assign a higher altitude to an aircraft in aviation communication. This phrase specifies both the action of climbing and the intended altitude that the pilot should maintain once they reach it.

Effective communication is critical in aviation to ensure clarity and safety. The term "climb and maintain" is well understood within the aviation community, and it provides unambiguous instructions to pilots, thereby minimizing the chance for misinterpretation. This phrase also adheres to the standardized phraseology provided by aviation authorities, ensuring consistency across various contexts and enhancing overall safety in flight operations.

The other responses may not provide the same level of clarity or may not be part of the standardized phraseology. For instance, saying "Proceed to climb now" could be interpreted in different ways, and "Ascend to a higher altitude" lacks specificity about what altitude the aircraft should maintain after the climb. Meanwhile, "Move to next altitude" is similarly vague and does not conform to the established protocols used in air traffic control communication.