Only basic level instructions are detailed in this chapter. More comprehensive phrases are contained in subsequent chapters in the context in which they are most commonly used.

The precise phraseology used in the transmission and acknowledgement of climb and descent clearances will vary depending upon the circumstances, such as traffic density and the nature of the flight operations. However, care must be taken to ensure that misunderstandings are not generated as a consequence of the phraseology employed during these phases of flight. For example, levels may be reported as altitude, height or flight levels according to the phase of flight and the altimeter setting.

When a change is made to any part of a level clearance, the entire level clearance shall be re-stated.

In the following examples, the operations of climbing and descending are interchangeable and examples of only one form are given.

Once having been given an instruction to climb or descend, a further overriding instruction may be given to a pilot.

Occasionally, for traffic reasons, a higher than normal rate-of-climb or descent may be required