Section 39C. The commission is hereby authorized to expend such sums as may be appropriated for the purpose of reimbursing cities or towns for airport construction as provided in section thirty-nine F. Such reimbursements shall be subject to the provisions and restrictions of said section thirty-nine F and of section fifty-one K, and the commission may, without appropriation, receive and distribute such federal funds as may be available therefor; provided, that such expenditures are otherwise in accordance with law.