; or (ii) served a small hub airport with more than 900,000 passenger enplanements in calendar year 2021; (B) are either currently owned by the FAA or are constructed to FAA standards; and (C) operate within complex airspace, including airspace that serves air carrier, general aviation, and military aircraft. (3) Tower selection The number of air traffic control towers selected to participate in the pilot program established under paragraph (1) shall be determined based on the availability of funds for the pilot program and the interest of the airport sponsor related to such facility. (4) Controller retention With respect to any high-activity air traffic control tower selected to be converted under the pilot program established under paragraph (1), the Administrator shall appoint to the position of air traffic controller any air traffic controller who— (A) is employed at such air traffic control tower as of the date on which the Administrator selects such tower to be converted; (B) meets the qualifications contained in section 44506(f)(1)(A) of title 49, United States Code