The reason this is a problem is that he's trying to make a change to the outbound segment of the itinerary. If he were just trying to change the date of the return he could do it by paying a smaller fee (i.e. $150 or $200 for an international itinerary..providing there are Z's available in the Z bucket for his new return flights). But because he's changing the outbound flight the rule is that the entire itinerary must be re-booked using whatever fares are available at the time... and since there are no Z fares available this close in he's being forced to buy a C or D fare. This is a tough one... i'm assuming he can't fly back to PIT in order to catch his originating flight?