I have a few tickets hanging out there where I have flown the outbound and need to see about making a change to the return that involves parsing the routing rules carefully. This one is a BA ticket, but the rules interpretation is airline agnostic (so I'd ask mods to not move it to the BA forum, since I think the general routing expertise is probably here). I've called BA already and they were helpless, so before I push to escalate, I need to confirm my reading of the "Transfers" and "flight application" sections of the rules.

I am currently booked SEA-LHR-GVA-LHR-SEA, the fare is I class and it has a $400 change/reissue fee. I'd like to change the return to GVA-LHR-YVR-SEA(AS), since the YVR flight is a couple of hours later and gives me some time I need in London that afternoon.

Transfers:
Flight Application: (I have excerpted the only two sections that talk about Canada or Alaska Airlines specifically)
The AS flight from YVR would be in the 2xxx range, so that is not disallowed under the flights. Where I am hung up is on the transfers. The transfers section contemplates a connection in Canada, but it looks like it has to be:

1. to AC (not allowed under the flight rules),
2. to AA (no AA metal and AS operated not allowed under the flight rules),
3. to BA (BA doesn't seem to put a codeshare on the AS flights between YVR-SEA)
4. to WS (allowed under transfers, not prohibited by flight application, but the only WS numbered flight is a DL codeshare)
5. transfers to AS are not specifically called out (so I don't think that is allowed)

The WS coded DL flight seems like it should be allowed, there is nothing in the flight application that prohibits a WS coded, DL operated flight. Am I correct that I should be able to use the WS coded flight between YVR-SEA?

Also, what about the lack of a transfer to AS in Canada being specified in the transfer section, does that mean I cannot use the AS 2xxx series flight from YVR-SEA?

This situation is very tricky. It would be helpful if you posted the rules for voluntary changes as well. Quite often, those sections will restrict you from changing the routing (which is what you're trying to do).

To your question (and without validating available flights), it seems that based on the rules posted the WS coded DL flight should be allowed.

That being said, when I last tried to change a *A ticket under similar conditions (changing date, and attempted to change routing), I was restricted in my choices to only codeshares of the ticketing carrier (AC). And I couldn't select a routing that differed from the original, no matter how hard the travel agent tried.

I'm a *A flyer, not OW so don't know how BA would deal with this, but I'd look at trying a "same day change". *A carriers often allow you to change the flights/routing after midnight on day of departure for a nominal fee. That might achieve your objective as you're not trying to change the date.

Thanks, in the end the person I spoke with said the fare was not valid to transit through Canada. But that seemed made up, the reality is that when I was booking this fare it actually showed some routings via YVR and YYC, using AS for the connection. So I just gave up and booked for the direct SEA flight the following day, which they finally figured out how to manually process.

My experience was similar. The fare rules and routings at the time of booking don't seem to have any relation with changes made after departure... :-(

Just because you saw routings through Canada when you booked doesn't mean those routings had the same fare rules. Could be, but doubtful.

They were in fact the exact same fare basis, that I confirmed when doing original searches.