Jesus explained that John the Baptizer fulfilled the prophecy about Elijah returning.

Matthew 17:9-13

9 When they were walking down the mountain, Jesus commanded them, “Do not tell anyone what you saw on the mountain top until God has caused me, the one who has come from heaven, to become alive again after I die.” 10 Those three disciples had just seen Elijah and he did not do anything to prepare people for the coming of the Messiah, so they asked Jesus, “If what you say is true, why do the men who teach the Jewish laws say that it is necessary for Elijah to come back to earth before the Messiah comes?” 11 Jesus answered them, “It is true that God promised that Elijah would come to prepare many [HYP] people for the Messiah’s coming. 12 But note this: Elijah’s representative has already come, and our leaders have seen him, but they did not recognize him as the one who would come before the Messiah. Instead, they treated him badly, just like they desired. And those same rulers will soon treat me, the one who came from heaven, in the same manner.” 13 Then the three disciples understood that when he was talking about Elijah, he was referring to John the Baptizer.