1. If you miss the plane (you should have left today, but you didn't board the plane because of something) and the ticket is valid.

(1) How to reschedule the ticket? You can change it to the date you want (sometimes charge, sometimes no charge); Some tickets can't be used (invalidated) once they miss the plane.

(2) If the itinerary has been used, the return flight has been missed or you want to postpone it, you can call the ticket office and ask if the ticket you bought can be rescheduled or postponed.

How do you buy this ticket has expired and most of it is invalid. For example, a plane ticket is valid for one year. You bought this plane ticket and remember it two years later. Then this ticket is basically unusable.