Couldn't find this answered in a search.

In trying to book a flight to Lisbon, I want to make certain I can upgrade to C for the Transatlantic portions and use my SWUs.

I can find the flights and all are ticketable in upgradeable fare buckets. All are on UA metal, however the transatlantic segment on the inbound is UA metal but a LH ticket/flight number.

Question is, will I be able to use an SWU on flight?

Any experience or thoughts are appreciated.