By a resolution adopted by a four-fifths vote of its members, the board may determine that the acquisition by purchase, condemnation, lease, or otherwise of real or personal property for the construction and completion of improvements necessary and convenient for any of the following purposes is of general county interest, and that county aid shall be extended for:

1. (a) The maintenance of airports owned and operated by cities.
2. (b) The flying and landing of aircraft.
3. (c) The maintenance of hangars, mooring masts, flying fields, and places for flying, take-off, landing, and storage of aircraft, together with signal lights, radio equipment, service shops, conveniences, appliances, works, structures, and other aircraft facilities now known or hereafter invented.