1. All airport zoning regulations adopted under sections 67.1200 to 67.1222 shall be reasonable and none shall impose any requirement or restriction which is not necessary to effectuate the purposes of sections 67.1200 to 67.1222.

2. No airport zoning regulations adopted under sections 67.1200 to 67.1222 shall require the removal, lowering, or other change or alteration of any structure or tree, or interfere with any use, not conforming to the regulations when adopted or amended, except that they may require the owner thereof to permit the municipality at its own expense to install, operate, and maintain thereon such markers and lights as may be necessary to indicate to operators of military aircraft the presence of the airport hazard.

3. All such regulations shall provide that no preexisting nonconforming structure, tree, or use, shall be replaced, rebuilt, altered, allowed to grow higher, or replanted, so as to constitute a greater airport hazard than it was when such airport zoning regulations or amendments thereto were adopted.