Provided further , That funds provided under this heading in this Act shall only be available to sponsors of airports in categories defined in section 47102 of title 49, United States Code: Provided further , That the requirements of chapter 471 of such title, except for project eligibility, shall apply to funds provided for any contract awarded (after the date of enactment of this Act) for airport development and funded under this heading: Provided further , That funds provided under this heading in this Act may not be used for any purpose not directly related to the airport: Provided further, That of the amounts appropriated under this heading in this Act— (1) Not less than $500,000,000 shall be to pay the local share of eligible costs for which a grant is made under this heading under the Department of Transportation Appropriations Act, 2021: Provided , That any remaining funds after the apportionment under this paragraph (1) shall be distributed as described in paragraph (2) under this heading in this Act: (2) Not less than $12,500,000,000 shall be available for any purpose for which airport revenues may lawfully be used: Provided , That such funds shall be allocated among eligible primary airports (as defined in section 47102(16) of title 49 United States Code) based on each airport’s calendar year 2019 enplanements as a percentage of total 2019 enplanements for all eligible primary service airports: Provided further , That sponsors provide relief equaling at least 25 percent of the amount allocated to an airport under this paragraph to on-airport car rental, on-airport parking, and in-terminal airport concessions (as defined in part 23 of title 49, Code of Federal Regulations) in the form of waiving rent, minimum annual guarantees, lease obligations, fees, or penalties, or, at the request of the owner of an in-terminal concession, to provide for a buyout of such concession: Provided further , That the sponsor shall give the highest priority to an owner who qualifies as an small businesses with maximum