14 CFR 221.53 : Aeronautics And Space (§ 1.1 To Parts 1311-1399) — (§ 200.1 To Parts 461-1199) — Office Of The Secretary, Department Of Transportation (Aviation Proceedings) (§ 200.1 To § 399.120) — Economic Regulations (§ 200.1 To § 298.80) — Tariffs (§ 221.1 To § 221.600) — Requirements Applicable To All Statements Of Fares And Charges (§ 221.50 To § 221.56) — Proportional fares.

(a) Definite application. Add-on fares shall be specifically designated as “add-on” fares on each page where they appear.

(b) A tariff may provide that fares from (or to) particular points shall be determined by the addition of add-ons to, or the deduction of add-ons from, fares therein which apply from (or to) a base point. Provisions for the addition or deduction of such add-ons shall be shown either directly in connection with the fare applying to or from the base point or in a separate provision which shall specifically name the base point. The tariff shall clearly and definitely state the manner in which such add-ons shall be applied.

(c) Restrictions upon beyond points or connecting carriers. If an add-on fare is intended for use only on traffic originating at and/or destined to particular beyond points or is to apply only in connection with particular connecting carriers, such application shall be clearly and explicitly stated directly in connection with such add-on fare.