How to upgrade a codeshare flight
 

One segment (FRA - SIN) of a RTW in business class is on Signapore Airlines booked under a LH codeshare flight number (LH9762). The whole RTW was booked through UA where I have most of my miles accumulated. I do have miles at M&M as well. How can I upgrade this segment?

No upgrade on SQ with UA miles I am afraid.

Looks possible with LH Miles & More according to the *A web site:
http://www.staralliance.com/en/trave...de_awards.html

However, this may be LH's out - "upgrades are subject to certain fare class and availability conditions with the participating programmes and carriers"

However, if they won't do the codeshare, you could always have the ticket re-issued (and pay the fee) but I'd check there is availability first!

A segment on a *A RTW in a codeshare?

No upgrade possible on code-share
 

I'm afraid to inform you that you will not be able to upgrade a code-share flight.

http://www.flyertalk.com/forum/showthread.php?t=677079

Krect™. Which means that the OP will need to have the ticket re-issued with that flight on the SQ code, as Markie suggested.

Yes quite allowable as long as operating airline is *A and not in an excluded flight number range.

On my latest RTW I had a couple of codeshares since no availability in business under the operating airline code but there was availability on the codeshare.

I dont think the ticket needs to be re-issued. AFAIK you can change carriers (keeping routing and date the same) and just revalidate without reissue.

That's what I thought too, but having no personal experience doing just that, I deferred to the previous poster ;)

Thanks for setting me straight ^

yep, no reissue... change of carriers is no problem at all. OP should just call UA to have that done and then upgrade...

good luck finding availability on SQ FRA-SIN though :D