Voluntary switching of routing due to oversold flight?
 

UA837 SFO to NRT on 09/14 at 11:35 a.m. currently supposedly oversold and UA 853 at 1:35 p.m. only showing C3, Y2, B2. Could one voluntarily switch routing to connect to UA875 SEA to NRT?

1K in Y with SWU I was hoping would clear - better to stay on original flight or try and switch routing? SEA flight shows C9. Also, first flight does not originate in SFO but there are connections through to SEA.

IMhO, not likely... but if they are desprate anything is possibale.

Since this is a few days in advance, I'm not sure what they would do if you tried calling now.

However on a recent ORD-DEN flight, one of the GAs was proactively rebooking people to nonstops available from ORD instead of their original routing (connecting in DEN). This was due to an oversold situation and allowed them to send the flight out without VDBs.

You'll likely have to wait till the day of to see if this sort of thing would be an option for you, though. But GAs will and can do pretty much whatever they need to do to get the flight out if it's oversold.

it depends
 

I think it just depends on the GA, so you'd have to just do it at the airport. I did this exact thing last week when my IAD-FCO flight was oversold - I was booked in Y. Told the GA I'd be happy to give up my seat if she put me in C from IAD to FRA (preferred) or MUC connecting onto FCO. She gladly did this and I got to try out the new C as well!

I have had luck switching from a waitlisted C flight (881 ORD-NRT) to a comfirmed C that had upgrade availability (883) with SWU upon airport check in - and neither flight was busy.

Your approach can make all the difference IMO.

The 9/14 flights SFO-NRT are only a little oversold, so they're not going be desperate yet. It looks iffy whether they'll actually DB anyone.

I'll bet you won't get anywhere on the phone now, but if you do please report back. Maybe you can switch at check-in.

Your upgrade chances look much better on SEA to NRT. But if it doesn't clear, you might end up in a worse Y seat (assuming you reserved a good one SFO-NRT).