14 C.F.R. § 221.31
Rules and regulations governing passenger fares and services
(a) Tariff rules and regulations governing passenger fares and services other than those subject to § 221.30 may be filed electronically in conformity with subpart R. Such filings shall conform to criteria approved by the Department's Office of International Aviation as provided in § 221.180 and shall contain at a minimum the information required by § 221.202(b)(9).
(b) Applications for special tariff permission may be filed electronically, as provided in § 221.212.
(c) Tariff publications and applications for special tariff permission covered by paragraphs (a) and (b) of this section may be filed in a paper format, subject to the requirements of this part and Department orders.