How Does 'Fare Difference' Work?
 

Suppose I have a unrestricted ticket. It allows free changes and cancellations and says "fares must be recalculated using historical fares in effect on purchase date" (or words to that effect) in the rules.

If I have a J class A-B-C-B-A ticket and have flown A-B-C already and want to change the return date for C-B-A, how would the new fare be calculated?

I always thought that there was no fare difference if the fare class stays the same but are there times this isn't true?

Do the airlines have a computer that can actually calculate what I would have paid for A-B-C-B-A on my new C-B-A travel dates if I had booked it way back when I did?

I tried to change the ticket from Expedia, where I booked it. Their idea was to issue me a 'new' C-B-A ticket (for 5x what I paid for my original A-B-C-B-A ticket) and to give me the residual value for my original ticket (which was zip, the RT was cheaper than the OW).

Then I called the airline, AA, who kept giving me a $3,000 fare difference. If I had booked the ticket on my new date, I know
the fare would have been exactly the same; when I was originally booking, I checked prices with both return dates, because I knew I might have to change it to the new date. They were the same.

The fare class is the same, the flights are the same, so what gives? I am assuming there is something I am missing?

Thanks!

Bump - I had delayed the trip but now I really need to use up the ticket.

Would asking to speak to a manager help?

Was the original ticket international?
You might need the entire rules and not just the historical fares bit. Even J class fare basises can carry min/max stay, seasonality,advance purchase that would trigger the repricing at current fares

And also historical doesnt just mean 'what you would have paid when you booked'. The original class of service for all segments has to be available today

Recently changed dates on a similar booking with Cathay and there was no repricing involved. As long as there was availability showing in "I" bucket, I could switch to any combination of Cathay flights taking me from C to A via B

Max stay was 12MO and the outbound was flown in July and there are no seasonal restrictions. The exact same fare is still available.

And there are seats in the original fare class for all segments yet I am being charged $600.

ps after waiting on hold for 92 minutes for a supervisor she was useless and darn right rude. I took this as an expensive lesson to stick with a travel agent next time.

When you got to C, instead of keeping the reservation 'active', by exchaning the ticket for a later return date, did you completely cancel the returning flights?

That may vary well be what's trigerring the repricing. If more than one agent+supvisor quoted you a fare difference, then that means there is some rule somewhere that you are not respecting.

When I have rebooked ticket, the fare is based on A - the price you paid and B- the price of that ticket as if it were new today.

You say you have a J class ticket - do you have a J fare? Or are you using the term to mean a business class ticket? Because within business there are different fare buckets - if the one you booked is sold out, then the higher fare bucket would incur the fee. It might be that one of the legs that fare bucket is sold out, meaning the extra charge.