; . (b) Authority to make agreements Section 41743(e)(1) of title 49, United States Code, is amended by adding at the end the following: The Secretary may amend the scope of a grant agreement at the request of the community or consortium and any participating air carrier, and may limit the scope of a grant agreement to only the elements using grant assistance or to only the elements achieved, if the Secretary determines that the amendment is reasonably consistent with the original purpose of the project. (c) Authorization of appropriations Section 41743(e)(2) of title 49, United States Code, is amended to read as follows: (2) Authorization of appropriations There is authorized to be appropriated to the Secretary $10,000,000 for each of fiscal years 2018 through 2023 to carry out this section. Such sums shall remain available until expended. . 456. Waivers Section 41732 is amended by adding at the end the following: (c) Waivers Notwithstanding section 41733(e), upon request by an eligible place, the Secretary may waive, in whole or in part, subsections (a) and (b) of this section or subsections (a) through (c) of section 41734. A waiver issued under this subsection shall remain in effect for a limited period of time, as determined by the Secretary. . 457. Extension of final order establishing mileage adjustment eligibility Section 409(d) of the Vision 100—Century of Aviation Reauthorization Act ( 49 U.S.C. 41731 note) is amended by striking 2018 and inserting 2023 . 458. Reduction in subsidy-per-passenger Section 426 of the FAA Modernization and Reform Act of 2012 (126 Stat. 98) is amended by adding at the end the following: (d) Reduction in subsidy-per-passenger (1) In general The Secretary shall waive application of the subsidy-per-passenger cap described under subsection (c) if the Secretary finds that the community’s subsidy-per-passenger for a fiscal year is lower than the subsidy-per-passenger for any of the 3 previous fiscal years. (2) Exception The Secretary shall waive application of the