Originally Posted by
davetravels
Wouldn't it be cheaper to change the ticket to return a day later before the currently booked flight departs? I would think that, in theory, after the flight departs, he'd have to buy a new ticket from scratch. But to change it before the departure of the original flight that he's going to miss, should just be a change fee plus possible additional fare, which I would think would be much cheaper than buying a new ticket from scratch.
Many airlines do make a ticket invalid if it isn't cancelled/changed before departure but AFAIK DL doesn't do this. However, it could depend on the fare rules as well as point of origin/sale.