Whenever any city or town undertakes, in conformity with the state airport plan, the acquisition, construction, establishment, enlargement, improvement or protection of an airport and has appropriated sufficient funds, which together with funds available under this section, shall equal at least fifty per cent of the cost thereof, the state treasurer, at the request of the commission, shall pay to or reimburse such city or town from such funds as have been appropriated for such purposes, such amount, not exceeding forty per cent of the cost of such work, as may be determined by the commission.
If any such city or town appropriates sufficient funds, which, together with the funds available under this section, is equal to one hundred per cent of the cost thereof, the state treasurer, at the request of the commission, shall pay to or reimburse such city or town from such funds as have been appropriated for such purpose, such amount, not exceeding fifty per cent of the cost of such work, as may be determined by the commission.