; and (2) the total amount invested in NextGen technologies and resulting quantifiable benefits on a quarterly basis until the Administrator announces the completion of NextGen implementation. 604. Airspace access (a) Coalescing airspace (1) Review of national airspace system Not later than 3 years after the date of enactment of this Act, the Administrator, in coordination with the Secretary of Defense, shall conduct a comprehensive review of the airspace of the national airspace system, including special use airspace. (2) Streamlining and expediting access In carrying out paragraph (1), the Administrator shall identify methods to streamline, expedite, and provide greater flexibility of access to certain categories of airspace for users of the national airspace system who may not regularly have such access. (b) Briefing (1) In general Not later than 3 months after the completion of review the under subsection (a), the Administrator shall brief the appropriate committees of Congress on the findings of such review and a proposed action plan to improve access to airspace for users of the national airspace system. (2) Contents In the briefing under paragraph (1), the Administrator shall include, at a minimum, the following: (A) An identification of current challenges and barriers faced by airspace users in accessing certain categories of airspace, including special use airspace. (B) An evaluation of existing procedures, regulations, and requirements that may impede or delay access to certain categories of airspace for certain users of the national airspace system. (C) Actions for streamlining and expediting the airspace access process, including potential regulatory changes, technological advancements, and enhanced coordination among relevant stakeholders and Federal agencies. (D) If determined appropriate, an implementation plan for a framework that allows for temporary access to certain categories of airspace, including special use airspace, by users of the national airspace system who do not have regular access to