No common carrier by aircraft shall abandon or discontinue any route, or part thereof, for which a certificate has been issued by the commission, unless upon the application of such common carrier, after notice and opportunity for hearing, the commission shall find such abandonment or discontinuance to be in the public interest. Any interested person may file with the commission a protest or memorandum of opposition to or in support of any such abandonment. The commission may, by regulation or otherwise, authorize such temporary suspension of service as may be in the public interest.