; Flexible Air Permitting Rule published by the Environmental Protection Agency in the Federal Register on October 6, 2009 (74 Fed. Reg. 51418)) with respect to such critical energy resource facility; and (2) facilitate flexible, market-responsive operations (as described in the final rule identified in paragraph (1)) with respect to critical energy resource facilities. (b) Definitions In this section: (1) Critical energy resource The term critical energy resource means, as determined by the Secretary of Energy, any energy resource— (A) that is essential to the energy sector and energy systems of the United States