(a) A concurrence prepared in a manner acceptable to the Office of International Aviation shall be used by a carrier to give authority to another carrier to issue and file with the Department tariffs which contain joint fares or charges, including provisions governing such fares or charges, applying to, from, or via points served by the carrier giving the concurrence. A concurrence shall not be used as authority to file joint fares or charges in which the carrier to whom the concurrence is given does not participate, and it shall not be used as authority to file local fares or charges.

(b) Number of copies. Each concurrence shall be prepared in triplicate. The original of each concurrence shall be filed with the Department, the duplicate thereof shall be given to the carrier in whose favor the concurrence is issued, and the third copy shall be retained by the carrier who issued the concurrence.

(c) Conflicting authority to be avoided. Care should be taken to avoid giving authority to two or more carriers which, if used, would result in conflicting or duplicate tariff provisions.

(a) A concurrence may be revoked by filing with the Department a Notice of Revocation of Concurrence prepared in a form acceptable to the Office of International Aviation.

(b) Sixty days' notice required. Such Notice of Revocation of Concurrence shall be filed on not less than sixty days' notice to the Department. A Notice of Revocation of Concurrence will be deemed to be filed only upon its actual receipt by the Department, and the period of notice shall commence to run only from such actual receipt.

(c) Number of copies. Each Notice of Revocation of Concurrence shall be prepared in triplicate. The original thereof shall be filed with the Department and, at the same time that the original is transmitted to the Department, the duplicate thereof shall be sent to the carrier to whom the concurrence was given. The third copy shall be retained by the carrier issuing such notice.

(d) Amendment of tariffs when concurrence revoked. When a concurrence is revoked, a corresponding amendment of the tariff or tariffs affected shall be made by the issuing carrier of such tariffs, on not less than statutory notice, to become effective not later than the effective date stated in the Notice of Revocation of Concurrence. In the event of failure to so amend the tariff or tariffs, the provisions therein shall remain applicable until lawfully canceled.

If a carrier desires to issue a concurrence conferring less authority than a previous concurrence given to the same carrier, the new concurrence shall not direct the cancellation of such previous concurrence. In such circumstances, such previous concurrence shall be revoked by issuing and filing a Notice of Revocation of Concurrence in a form acceptable to the Office of International Aviation. Such revocation notice shall include reference to the new concurrence.