; (ii) had fewer than 10,000 passenger boardings during the calendar year used to calculate the apportionment for fiscal year 2018, 2019, or 2020, as applicable, under subparagraph (A); and (iii) had scheduled air service at any point in the calendar year used to calculate the apportionment. (G) Limitations and waivers The authority to make apportionments in the manner prescribed in subparagraph (F) may be utilized no more than 3 years in a row. The Secretary may waive this limitation if the Secretary determines that an airport’s enplanements are substantially close to 10,000 enplanements and the airport sponsor or affected communities are taking reasonable steps to restore enplanements above 10,000. (H) Minimum apportionment for commercial service airports with more than 8,000 passenger boardings in a calendar year Not less than $600,000 may be apportioned under subparagraph (A) for each fiscal year to each sponsor of a commercial service airport that had fewer than 10,000 passenger boardings, but at least 8,000 passenger boardings, during the prior calendar year. . 152. Construction of certain control towers Section 47116(d) of title 49, United States Code, is amended by adding at the end the following: (3) Control tower construction Notwithstanding section 47124(b)(4)(A), the Secretary may provide grants under this section to an airport sponsor participating in the contract tower program under section 47124 for the construction or improvement of a nonapproach control tower, as defined by the Secretary, and for the acquisition and installation of air traffic control, communications, and related equipment to be used in that tower. Such grants shall be subject to the distribution requirements of subsection (b) and the eligibility requirements of section 47124(b)(4)(B). . 153. Nondiscrimination Section 47123 of title 49, United States Code, is amended— (1) by striking The Secretary of Transportation and inserting the following: (a) In general The Secretary of Transportation