; and (ii) before applying the rates under the modified or alternative system to underwater products, shall comply with subparagraph (A). (C) Rule of construction Nothing in this paragraph shall be construed to affect the requirement under subsection (a) relating to reinstatement of the rate surcharge that was in effect on April 9, 2016, including with respect to underwater products. (d) Postal Regulatory Commission authority not affected Nothing in this section (other than subsection (c)) shall be construed as affecting the authority of the Commission to, by regulation, make such modification or adopt such alternative system for regulating rates and classes for market-dominant products as provided under section 3622 of title 39, United States Code. 208. Review of Postal Service cost attribution guidelines Not later than April 1, 2019, the Commission shall initiate a review of the regulations issued pursuant to sections 3633(a) and 3652(a)(1) of title 39, United States Code, to determine whether revisions are appropriate to ensure that all direct and indirect costs attributable to competitive and market-dominant products are properly attributed to those products, including by considering the underlying methodologies in determining cost attribution and considering options to revise such methodologies. If the Commission determines, after notice and opportunity for public comment, that revisions are appropriate, the Commission shall make modifications or adopt alternative methodologies as necessary. 209. Aviation security for parcels Not later than 18 months after the date of enactment of this Act, the Inspector General of the Postal Service shall transmit to the Committee on Oversight and Government Reform of the House of Representatives and the Committee on Homeland Security and Governmental Affairs of the Senate the results of a review of the security measures in place for parcels carried on air carriers to domestic and international destinations for which audit trails are generated. The review required under