It is the policy of the Board to limit the duration of exemptions which authorize fixed-term route service to a maximum period of two years, and to entertain requests for renewal of such authority only when incorporated in a duly filed application for substantially equivalent certificate authority under section 401 of the Act. (See Sec. 377.10(c) of this chapter (Special Regulations).) [PS-21, 29 FR 1446, Jan. 29, 1964, as amended at 65 FR 6457, Feb. 9, 2000] Sec. 399.19 [Reserved]