I currently have a Business class ticket from VIE to HKG (via LHR). The departure is in April, and return in July. I would actually now like to return to ARN instead of VIE.
I called the BA Gold line to ask how much it would be to make this change, and it was some large amount like 350 GBP.
I have read elsewhere here that if I ring to re-route after the outgoing sector has been flown that it's possible that I can re-route with minimal change fees as they won't re-price the ticket then.
If you're only changing from VIE-LHR-HKG-LHR-VIE to VIE-LHR-HKG-LHR-ARN, then it seems to me that you're unlikely to be saving any money by waiting until after departure to make the change.
The reason is this: If you make a change to the first fare component now (ie before departure), then you will have the entire journey repriced at current fares. However, the usual fare rules provide that if you make a change now that does
not involve changing the first fare component, then you will be repriced using
either historical fares
or current fares, whichever is cheaper.
Your ticket is probably fared using two fare components: VIE-HKG and HKG-VIE. The change you want to make will probably result in you having a ticket fared using VIE-HKG and HKG-ARN fare components. In other words, you're not wanting to change the first fare component, and so if you make the change now you can be repriced using historical fares if that is cheaper than using current fares.
The change fee will always be payable, whenever you do the change.