JO 7110.65 2-1-5

Use the word “immediately” only when expeditious compliance is required to avoid an imminent situation.

Use the word “expedite” only when prompt compliance is required to avoid the development of an imminent situation. If an “expedite" climb or descent clearance is issued by ATC, and subsequently the altitude to maintain is changed or restated without an expedite instruction, the expedite instruction is canceled.

In either case, if time permits, include the reason for this action.