(a) Each carrier required to file tariffs in accordance with this part shall make available to any person so requesting a subscription service as described in paragraph (b) of this section for its passenger tariffs issued by it or by a publishing agent on its behalf.

(b) Under the required subscription service one copy of each new tariff publication, including the justification required by § 221.94, must be transmitted to each subscriber thereto by first-class mail (or other equivalent means agreed upon by the subscriber) not later than one day following the time the copies for official filing are transmitted to the Department. The subscription service described in this section shall not preclude the offering of additional types of subscription services by carriers or their agents.

(c) The carriers or their publishing agents at their option may establish a charge for providing the required subscription service to subscribers: Provided, That the charge may not exceed a reasonable estimate of the added cost of providing the service.