flier vs airman

flier and airman both are nouns.

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

As nouns, airman is a hyponym of flier; that is, airman is a word with a more specific, narrower meaning than flier:

Other hyponyms of flier include airwoman, aviatress, aviatrix, airplane pilot, pilot.

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