What is the proper phraseology for instructing an ascent to a higher altitude from a lower one?

The phrase "Climb and maintain (altitude)" is the proper phraseology for instructing an aircraft to ascend from a lower altitude to a higher one. This directive clearly communicates the intention for the pilot to increase altitude and maintain that new altitude once reached. It is clear and unambiguous, which is crucial for safety and efficiency in air traffic control communications.

Using this phraseology ensures that the pilot knows they are required to actively climb to the specified altitude and to hold that altitude once established. This instruction reflects accepted aviation standards and practices, providing pilots with a straightforward command they can easily follow.

Additionally, the phraseology emphasizes both the action of climbing and the requirement to maintain the altitude thereafter, which is essential for airspace management and separation between aircraft.