Whenever there shall be filed with the Commission any schedule stating a new individual or joint rate, fare, charge, or classification for the transportation of passengers or property by a common or restricted common carrier by aircraft, or by any such carrier in conjunction with a common carrier by railroad, motor vehicle, express and/or water, or any rule, regulation, or practice affecting such rate, fare, or charge, or the value of the service thereunder, the Commission, upon complaint of any interested party or upon its own initiative, if it so orders, without answer or other formal pleading by the interested carrier or carriers, but upon reasonable notice, may enter upon a hearing concerning the lawfulness of such rate, fare or charge, or such rule, regulations or practice.

Pending such hearing and the decision thereon the Commission, by filing with such schedule and delivering to the carrier or carriers affected thereby a statement in writing of its reasons for such suspension, may suspend the operation of such schedule and defer the use of such rate, fare, or charge, or such rule, regulation, or practice, for a period of 90 days and if the proceeding has not been concluded and a final order made within such period the Commission may, from time to time, extend the period of suspension by order, but not for a longer period in the aggregate than 180 days beyond the time when such rate, fare, charge, rule, regulation or practice would otherwise go into effect.

After such hearing, whether completed before or after the rate, fare, charge, classification, rule, regulation, or practice goes into effect, the Commission may make such order with reference thereto as would be proper in a proceeding instituted after it had become effective. If the proceeding has not been concluded and an order made within the period of suspension, the proposed change of rate, fare or charge, or classification, rule, regulation, or practice, shall go into effect at the end of such period.