14 CFR 323.14: Temporary suspension authority for involuntary interruption of service.

(a) Any air carrier may temporarily suspend service without filing a notice under § 323.3 for any interruption of service that the carrier cannot reasonably be expected to foresee or control, such as rules, standards, or other action, or inaction, of the Administrator of the Federal Aviation Administration or of a foreign government, emergency measures, strikes, weather conditions, construction work on airports, or disasters. However, the provisions of this paragraph shall apply to interruptions due to airport inadequacies only if the carrier is unable to serve the place through any airport convenient to the place with the type of equipment last regularly used to serve the place.

(b) In the case of an interruption of service caused by a strike, the carrier shall give immediate notice of the interruption to DOT. Suspension authority under this section due to a strike shall expire 90 days after employees return to work.

(c) If service to a place is interrupted for more than 3 consecutive days for reasons beyond the carrier's control other than a strike, the holder shall give notice to DOT within 3 days following the date of first interruption, setting forth the date of first interruption and a full statement of the reasons for the interruption.

(d) The notice required by paragraph (b) or (c) of this section shall be marked for the attention of the Director, Office of Aviation Analysis.