They are unions in the sense that they draw their funding from membership fees, set high entry standards that keep competition in check for existing members (obviously there are altruistic reasons for this too, but one impact of requiring a long, expensive degree is low competition). The union structures in medicine and law and piloting tends to favor established members over new ones.

IMO setting high standards is a quality shared by any healthy industry, because permitting shoddy work means every consumer needs to learn the details of the task in order to judge their provider.