; or (ii) is at an airport receiving an exemption under section 47134. (5) Authorization (A) In general There is authorized to be appropriated to the Secretary to carry out this subsection the following amounts: (i) $1,020,000,000 for fiscal year 2019. (ii) $1,041,000,000 for fiscal year 2020. (iii) $1,064,000,000 for fiscal year 2021. (iv) $1,087,000,000 for fiscal year 2022. (v) $1,110,000,000 for fiscal year 2023. (B) Availability Sums authorized to be appropriated under subparagraph (A) shall remain available for 2 fiscal years. . 138. Safety equipment Section 47102(3)(B)(ii) of title 49, United States Code, is amended by striking and emergency call boxes, and inserting emergency call boxes, and counter-UAS systems (as defined in section 40102), . 139. Use of airport improvement funds to prevent power outages Section 47102(3) of title 49, United States Code, is amended by adding at the end the following: (P) an on-airport project to purchase and install generators to prevent power outages in the passenger areas of the airport, separate an airport’s redundant power supply and its main power supply, or prevent power outages in the airport or damage to the airport’s power supply. . 140. General written assurances Section 47107(a)(17) of title 49, United States Code, is amended by striking each contract and inserting if any phase of such project has received funds under this subchapter, each contract . 141. Construction of certain control towers Section 47116(d) of title 49, United States Code, is amended adding at the end the following: (3) Control tower construction Notwithstanding any provision of section 47124(b)(4)(A), the Secretary may provide grants under this section to an airport sponsor 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