Such special fund shall be expended and disbursed by order of the Department, through the medium of warrants drawn by the Comptroller, for the reasonable and necessary costs of administration of the Department and for the planning, construction, maintenance and improvement of airports and landing fields, to which the public now has, or which it is proposed shall have, access, and for the promotion of aviation in the interest of operators generally. Such expenditures and disbursements may be in the form of grants or loans to such person or persons as may be, in the discretion of the Board, entitled thereto in the interest of the public. Such grants or loans shall be made under such terms and conditions, as may be fixed by the Board and, in the case of loans, the rate of interest and the terms of repayment thereof as may be fixed by the Board. In considering or evaluating the application for or award of any grant of moneys under this section, the Board shall take into account the capacities of all airports within the affected geographic region.