flypast vs fly-by

flypast and fly-by both are nouns.

Word	Noun	Adjective	Verb	Adverb
flypast	Yes	No	No	No
fly-by	Yes	No	No	No

As nouns, flypast and fly-by are synonyms defined as:

flypast and fly-by: a flight at a low altitude (usually of military aircraft) over spectators on the ground

Other synonyms of flypast include flyover.

flypast (noun)	fly-by (noun)
a flight at a low altitude (usually of military aircraft) over spectators on the ground	a flight at a low altitude (usually of military aircraft) over spectators on the ground