aeronaut vs flier

aeronaut and flier both are nouns.

Word	Noun	Adjective	Verb	Adverb
aeronaut	Yes	No	No	No
flier	Yes	No	No	No

As nouns, aeronaut and flier are synonyms defined as:

Other synonyms of aeronaut include aviator, flyer.

aeronaut (noun)	flier (noun)
someone who operates an aircraft	an advertisement (usually printed on a page or in a leaflet) intended for wide distribution
	someone who travels by air
	someone who operates an aircraft