clearance prefix

ref ) AIM

4-2-2

1. CLEARANCE PREFIX

1. Prefix a clearance, information, or a request for information which will be relayed to an aircraft through a non-ATC facility by stating “A-T-C clears,” “A-T-C advises,” or “A-T-C requests.”
2. Flight service stations and ARTCC Flight Data Units must prefix a clearance with the appropriate phrase: “ATC clears,” “ATC advises,” etc.