We are revising the regulations governing State and Federal operating permit programs required by title V of the Clean Air Act (CAA or the Act) to promote flexible air permitting (FAP) approaches that provide greater operational flexibility and, at the same time, ensure environmental protection and compliance with applicable laws. The revisions to our title V regulations consist of adding definitions for alternative operating scenario (AOS) and approved replicable methodology (ARM) and codifying some clarifications to existing provisions. These revisions are intended to clarify and reaffirm opportunities for accessing operational flexibility under existing regulations. We are not finalizing any revisions to our existing minor or major New Source Review (NSR) regulations. In particular, we are withdrawing that portion of the proposal which relates to Green Groups and their potential inclusion in NSR programs required by parts C and D of title I of the Act. Instead, we are encouraging States and sources to investigate in more depth the flexibilities currently available under the major NSR regulations.