air travel vs travel

air travel and travel both are nouns.

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

As nouns, travel is a hypernym of air travel; that is, travel is a word with a broader meaning than air travel:

Other hypernyms of air travel include traveling, travelling.

air travel (noun)	travel (noun)
travel via aircraft	the act of going from one place to another
	self-propelled movement
	a movement through space that changes the location of something

air travel (verb)	travel (verb)
	change location; move, travel, or proceed, also metaphorically
	make a trip for pleasure
	travel upon or across
	undergo transportation as in a vehicle
	undertake a journey or trip
	travel from place to place, as for the purpose of finding work, preaching, or acting as a judge