line of flight vs route

line of flight and route both are nouns.

Word	Noun	Adjective	Verb	Adverb
line of flight	Yes	No	No	No
route	Yes	No	Yes	No

As nouns, route is a hypernym of line of flight; that is, route is a word with a broader meaning than line of flight:

line of flight: the path along which a freely moving object travels through the air
route: an established line of travel or access

Other hypernyms of line of flight include itinerary, path.

line of flight (noun)	route (noun)
the path along which a freely moving object travels through the air	an open way (generally public) for travel or transportation
	an established line of travel or access

line of flight (verb)	route (verb)
	send via a specific route
	divert in a specified direction
	send documents or materials to appropriate destinations