Originally Posted by xliioper

After a bit more investigation, I realized that TPAC PS fares are dual inventory fares (as are domestic and South America PS fares) and the Economy segment on KE just books in the underlying coach fare basis class of the PS fare. So you could potentially upfare to an M basis PS fare in order to get the KE segment into a DL M booking class and this is likely the only way it can be accomplished. But again, a M class seat requires KE O inventory, not just Z, to apply GUC.

I checked PS fares on the SLC-HKT route on EF and the cheapest one-way M basis PS fare is a MLE00NQ0 fare (PS segment books into G) goes for $1131 more than the cheapest one-way PS fare on route (a V basis VLE00NQW fare that likewise books into G in PS cabin). The cheapest B basis PS fare on route is a BLE00NQ0 fare which goes for nearly $2000 more than a VLE00NQW fare. A VLE00NQW fare on this route goes for $1246.40 with taxes/fees. So a MLE00NQ0 fare would be $2377.40 based on fare filings on EF.