air unit vs flight

air unit and flight both are nouns.

Word	Noun	Adjective	Verb	Adverb
air unit	Yes	No	No	No
flight	Yes	No	Yes	No

As nouns, flight is a hyponym of air unit; that is, flight is a word with a more specific, narrower meaning than air unit:

Other hyponyms of air unit include air division, division, wing, air group, squadron.

air unit (noun)	flight (noun)
a military unit that is part of the airforce	an instance of traveling by air
	the act of escaping physically
	a scheduled trip by plane between designated airports
	a stairway (set of steps) between one floor or landing and the next
	passing above and beyond ordinary bounds
	an air force unit smaller than a squadron
	a formation of aircraft in flight
	a flock of flying birds
	the path followed by an object moving through space