air travel vs put down

air travel is a noun but put down is not a noun.

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

air travel (noun)	put down (noun)
travel via aircraft

air travel (verb)	put down (verb)
	put down in writing; of texts, musical compositions, etc.
	make a record of; set down in permanent form
	put in a horizontal position
	remove (cargo, people, etc.) from and leave
	cause to sit or seat or be in a settled position or place
	put (an animal) to death
	reduce in worth or character, usually verbally
	cause to come to the ground