In the discretion of the Board any bonds issued under the provisions of this chapter may be secured by a trust agreement by and between the Board and a corporate trustee, which may be any trust company or bank having the powers of a trust company within or without the Commonwealth. Such trust agreement or the resolution providing for the issuance of such bonds may pledge or assign the revenues to be received, but shall not convey or mortgage any airport project or any part thereof. Such trust agreement or resolution providing for the issuance of such bonds may contain such provisions for protecting and enforcing the rights and remedies of the bondholders as may be reasonable and proper and not in violation of law, including covenants setting forth the duties of the Board in relation to the acquisition of property and the acquisition, construction, establishment, improvement, extension, enlargement, equipment, maintenance, repair, operation, and insurance of the airport project or projects in connection with which such bonds shall have been authorized, the rates and fees to be charged, the custody, safeguarding, and application of all moneys, and conditions or limitations with respect to the issuance of additional bonds. It shall be lawful for any bank or trust company incorporated under the laws of the Commonwealth which may act as depositary of the proceeds of bonds or of revenues to furnish such indemnifying bonds or to pledge such securities as may be required by the Board. Any such trust agreement may set forth the rights and remedies of the bondholders and of the trustee, and may restrict the individual right of action by bondholders. In addition to the foregoing, any such trust agreement or resolution may contain such other provisions as the Board may deem reasonable and proper for the security of the bondholders. All expenses incurred in carrying out the provisions of such trust agreement or resolution may be treated as a part of the cost of the operation of the airport project or projects.