; (B) will employ best business practices in developing or implementing a public-private partnership; or (C) has established, or will establish, a public-private partnership to build or improve facilities at the airport; or (2) the assistance will be used in a timely fashion. (e) Types of assistance The Secretary may use amounts made available under this section— (1) to provide assistance to market an airport to private entities or individuals in order to leverage private sector investments or develop public-private partnerships for the purposes of building or improving hangars, businesses, or other facilities at the airport; (2) to fund studies that consider what measures an airport should take to attract private sector investment at the airport; or (3) to participate in a partnership described in paragraph (1) or an investment described in paragraph (2). (f) Authority To make agreements The Secretary may enter into agreements with airports and entities entering into partnerships with airports under this section to provide assistance under this section. (g) Availability of amounts from Airport and Airway Trust Fund (1) In general There is authorized to be appropriated, out of the Airport and Airway Trust Fund established under section 9502 of the Internal Revenue Code of 1986, $5,000,000 for each of the fiscal years 2018 through 2021 to carry out this section. Amounts appropriated pursuant to this paragraph shall remain available until expended. (2) Availability Amounts appropriated pursuant to paragraph (1)— (A) shall remain available until expended