A CAMO may extend the ARC of an aircraft, during maintenance, with a partial CRS prior to the MCF (Maintenance Check Flight).

M.A.901(c)(2) and (f) allow the CAMO managing the aircraft to extend the ARC subject to the conditions of M.A.901(b), for controlled environment, and M.A.901(j), regarding the prohibition to extend the ARC if there is evidence that the aircraft is not airworthy.

The fact that the ARC expires during base maintenance and was subsequently extended after partial CRS prior to the MCF would not automatically imply that the aircraft was not in a controlled environment.

It may be acceptable for the ARC to be extended at the end of extended maintenance, but prior to the final release to service of the entire maintenance package, after all maintenance necessary to consider the aircraft ready for safe flight has been completed (e.g. to allow for a maintenance check flight when required by maintenance data, under its certificate of airworthiness with a certificate of release to service following incomplete maintenance as described in GM M.A.301(i)(b)(1)).