I actually flew on the 3/14 flight. It was really empty, like ~50 people flying on that 321 and everyone had a row to themselves.

Only 1 passenger was in the business class and they had pilots/crews occupying 3 business class seats.

Most people on that flight were Chinese immigrants/workers in Saipan going home. The T'way and Jeju Air flights were much more popular among Korean tourists.