Section 51K. Any airport commission established by law obtaining an offer for a grant of federal funds shall designate the Massachusetts aeronautics commission as its agent to receive federal moneys and receipt therefor in its behalf, and shall enter into an agreement with said last mentioned commission prescribing the terms and conditions of such agency in accordance with federal laws, rules and regulations and applicable laws of the commonwealth.

Every such airport commission may invite bids for any contract involving the acquisition, establishment, construction, enlargement, protection, equipment, maintenance or operation of an airport, the site for which has been approved as provided by section thirty-nine B, and shall submit every such proposed contract to said Massachusetts aeronautics commission for approval. After approval has been given, said airport commission may award such contracts; provided, that the liability incurred shall not exceed the funds available therefor, including the appropriation voted and the amount of any gift or bequest, together with the amount or amounts stated in any existing agreements for the allotment or grant of funds by the federal government or commonwealth, or both.

If a city or town shall have an agreement with the federal government or the commonwealth whereby such government or commonwealth grants such city or town a sum of money to be used, with funds provided by said city or town, for an airport, and shall be required primarily to pay that portion of the expense for which reimbursement is to be received from such grant, or grants, the treasurer of such city or town, with the approval of the mayor or selectmen, as the case may be, in anticipation of the proceeds of such grant, or grants, may incur debt, which shall be outside the debt limit, to an amount not exceeding the amount of the grant or grants, as shown by the grant agreement or agreements and may issue notes therefor payable in not more than two years from their dates. Any loan issued under this section for a shorter period than two years may be refunded by the issue of other notes maturing within the required period; provided, that the period from the date of issue of the original loan to the date of maturity of the refunding loan shall not be more than two years. The proceeds of the grant or grants, so far as necessary, shall be applied to the discharge of the loan.