Fares stated in percentages of other fares; other relationships prohibited.
(a) Fares for foreign air transportation of persons or property shall not be stated in the form of percentages, multiples, fractions, or other relationships to other fares except to the extent authorized in paragraphs (b), (c), and (d) of this section with respect to passenger fares and baggage charges.
(b) A basis of fares for refund purposes may be stated, by rule, in the form of percentages of other fares.
(c) Transportation rates for the portion of passengers' baggage in excess of the baggage allowance under the applicable fares may be stated, by rule, as percentages of fares.
(d) Children's, infants' and senior citizen's fares, may be stated, by rule, as percentages of other fares published specifically in dollars and cents (hereinafter referred to as base fares): Provided, that:
(1) Fares stated as percentages of base fares shall apply from and to the same points, via the same routes, and for the same class of service and same type of aircraft to which the applicable base fares apply, and shall apply to all such base fares in a fares tariff.
(2) Fares shall not be stated as percentages of base fares for the purpose of establishing fares applying from and to points, or via routes, or on types of aircraft, or for classes of service different from the points, routes, types of aircraft, or classes of service to which the base fares are applicable.