I booked a flight DOH-BKK in economy and used qcredits to upgrade from Y to J. On the day of the flight I saw that the F cabin was almost empty so I asked at the airport if I could upgrade to F. I was open to how this could be done: cash or miles and my decision would be depedent on how many miles I would have to use versus how much cash they wanted. I was told it was not possible given that I already upgraded from Y to J.
I am assuming this is correct, but I thought it was a bit strange to have a passenger willing to pay money to upgrade and the rules are such that he cannot do so. To fly in F on that day, I would have had to purchase a completely new ticket and forego the rest of my itinerary which is quite a bit to ask.
Would it not be in QR's best interest to allow people to pay to upgrade when they want to do so? It would essentially mean that I am changing my Y ticket to a J ticket, and that I am using my qcredits to upgrade from J to F rather than from Y to J. Or just give me back the qcredits and ask me to pay for the upgrade from Y to F based on the fare difference?
I was a bit disappointed by the lack of flexibility. Not the end of the world, but a bit surprising experience.