If you want to change the date, time and destination then you can make this perfect with Korean Air Ticket Change Policy. your tickets must be reissued and the charge or reissue of the ticket is $25.$150 is charged for reissue domestic flights and $200 Or more for international flight tickets. Some tickets are not allowed to make changes in booking even with a fee. https://airlinespolicy.com/flight-change-policy/korean-air-change-flight-policy/