Okay. I'm still not sure whether married segment availability is a thing with upgrade inventory, since they will clear upgrades by segment, but I'm going to run with the theory that it is not (and possibly be corrected).

For your dates, LAX-MEL and MEL-LAX are both wide open (R9). Any method of routing a GPU eligible fare onto those flights should clear at booking, regardless of your SFO connection. The SFO-LAX connections are anything but, and the system will display your upgrade availability using the following metric:

• if you are fared through SFO to MEL, it will take the set intersection of the R availability (so R0 intersect R9 is R0), apply it to both flights, and tell you there is no R space. Engine will claim "waitlist upgrade", but your TPAC segment should clear immediately (SFO-LAX will waitlist)
• if you have a fare break in LAX, it will show each segment correctly, and show "mixed upgrade" since one segment will clear

In both cases the TPAC should clear at booking. I'm about 95% sure of this - even if I'm wrong you should be able to cancel for free within 24 hours.


As I edited my above post to note, the one ways are cheaper because you can ticket ex-MEL with no YQ. This prices as SFO-MEL/MEL-LAX/LAX-SFO, which may give you different indications of R space as noted above. If you don't mind booking on separate tickets, you can do this to save a bit of money. Do not ask an agent to do this on one PNR; it will not work. But no matter your approach, and no matter which SFO connection you want, the important leg should clear into R at booking ^