(a) In any city of the first class, owning and operating a municipal airport and its related properties and facilities, by or through an airport board of commissioners, the commission is authorized to provide a plan for social security, old age pensions, or retirement pay for part or all employees of the airport and its related properties and facilities, under such plan as the commissioners may provide.
(b) If such a plan is not placed in effect, the seniority and retirement rights and benefits to which the airport personnel are entitled shall remain in full force and effect.