Within 30 days after the organization of such county airport commission, or within 30 days after a vacancy occurs in such office, the Commission shall submit a list of not less than 3 nor more than 5 names of persons to the Department, whom it considers desirable candidates for the office of Superintendent. Candidates shall have one or more of the following qualifications in order to be eligible to hold such office: First, shall be a civil engineer, having a degree from a reputable engineering school or a civil engineer recognized as such by a national professional society of engineers, or structural engineer licensed in this state, with an additional 4 years practical experience in highway, structural or airport engineering design and construction, Second, shall have had at least 10 years experience in highway, structural or airport engineering, 5 years of which have been spent in responsible charge of design and construction of such works. The Department shall thereupon determine by competitive examination from among the names submitted the person or persons best fitted for the office and shall thereupon certify its determination to the presiding officer of the county board of such county, who shall then make an order appointing, with the advice and consent of the county board, from the number found eligible, a County Superintendent of Airports for such county. If, on the list submitted, there is found only one person qualified for the position, the proceedings shall be repeated in a like manner until two or more persons eligible for such position has been determined.