I am one of those lucky ones who could take advantage of those cheap tickets originating from RGN.
One of those tickets I have is issued by Delta. For this ticket, the sectors from RGN to Europe are operated by Thai. The sectors between Europe to USA is with Delta.
Does anyone know if it is possible to upgrade those sectors by Thai using my Gold Upgrade even though the ticket is being issued by DL in this case?
Appreciate if you could share your experiences.
Update: ON second thought, maybe I should not be too greedy in case it alerts Thai and I will be denied boarding at the beginning. Just threat this as a therotical question then...