(a) The display of official notices used by any court, or public body or official, or the posting of notices by any public officer in the performance of a duty, or by any person giving legal notice.

(b) Directional, warning, or informational signs of a public or quasi-public nature, directed and maintained by an official body or public utility.

(c) Any sign of a noncommercial nature when used to protect the health, safety, or general welfare of the public.

(d) Any official flag, pennant, or insignia of any nation, state, City or other political unit.

(e) Any signs which convey only general navigation, flying conditions, or other information related to flight convenience or flight safety.