14 CFR 221.51: Territorial application.

(a) Specific points of origin and destination. Except as otherwise provided in this part, the specific points of origin and destination from and to which the fares apply shall be specifically named directly in connection with the respective fares.

(b) Directional application. A tariff shall specifically indicate directly in connection with the fares therein whether they apply “from” and “to” or “between” the points named. Where the fares apply in one direction, the terms “From” and “To” shall be shown in connection with the point of origin and point of destination, respectively, and, where the fares apply in both directions between the points, the terms “Between” and “And” shall be shown in connection with the respective points.