14 CFR § 121.127

Each certificate holder conducting supplemental operations using a flight following system must show that—

The system has adequate facilities and personnel to provide the information necessary for the initiation and safe conduct of each flight to—

The flight crew of each aircraft; and

The persons designated by the certificate holder to perform the function of operational control of the aircraft; and

The system has a means of communication by private or available public facilities (such as telephone, telegraph, or radio) to monitor the progress of each flight with respect to its departure at the point of origin and arrival at its destination, including intermediate stops and diversions therefrom, and maintenance or mechanical delays encountered at those points or stops.

The certificate holder conducting supplemental operations must show that the personnel specified in paragraph (a) of this section, and those it designates to perform the function of operational control of the aircraft, are able to perform their required duties.