I'm interested in a RT fare, e.g. AAA-BBB flight taken sometime in Sept.'20, and the return BBB-AAA in June '21. The RT fares are pretty good now, but I need to figure out if the fee waiver policy would be of any help. The intended return date can't even be booked now, so I'll need to change it before taking the return leg of the trip. If the change is requested after the trip is half-completed, how will UA determine if an extra charge is due for changing my return flight?