crew vs air crew

crew and air crew both are nouns.

Word	Noun	Adjective	Verb	Adverb
crew	Yes	No	Yes	No
air crew	Yes	No	No	No

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

Other hyponyms of crew include aircrew, merchant marine.

crew (noun)	air crew (noun)
an organized group of workmen	the crew of an aircraft
the men and women who man a vehicle (ship, aircraft, etc.)
the team of men or women manning a racing shell
an informal body of friends

crew (verb)	air crew (verb)
serve as a crew member on