It may be omitted from a clearance if the SID has the departure control frequency published on it.

• A. It must be included in every clearance
• B. It is always published in the SID
• C. It may be omitted when a frequency is published on the SID
• D. It may be omitted if the SID has the departure control frequency published on it

Answer: (D)

When a SID publishes the departure control frequency, that frequency can be omitted from the clearance. The reason is simple: the SID already provides the exact frequency you should use to contact departure after takeoff, so repeating it in the clearance would be redundant. This keeps the clearance concise and reduces radio chatter, while you still know where to contact once you’re airborne because the SID is your reference. If the SID does not publish a departure frequency, then the clearance would include the frequency to contact. The other options assume the frequency must always be in the clearance or that it’s always published on the SID, which isn’t guaranteed.