14 CFR 223.21: Free and reduced-rate transportation authorized by statute or regulation.

(a) Any air carrier or foreign air carrier may provide free or reduced-rate foreign air transportation to any classes of persons specifically named in 49 U.S.C. 41511 or free transportation to those named in § 375.35 of this chapter.

(b) Air carriers and foreign air carriers may offer reduced fares for foreign air transportation to ministers of religion, the elderly, retired, and handicapped passengers, and to attendants required by handicapped passengers, but shall file tariffs for such fares. Carriers may establish reasonable tariff rules to assist in identifying those who qualify for reduced fares.