airplane pilot vs flier

airplane pilot and flier both are nouns.

Word	Noun	Adjective	Verb	Adverb
airplane pilot	Yes	No	No	No
flier	Yes	No	No	No

As nouns, flier is a hypernym of airplane pilot; that is, flier is a word with a broader meaning than airplane pilot:

Other hypernyms of airplane pilot include aeronaut, aviator, flyer.

airplane pilot (noun)	flier (noun)
someone who is licensed to operate an aircraft in flight	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