Originally Posted by
flashware
I suppose it depends on whether the underlying ticket was cash or Avios purchased?
Originally Posted by
KARFA
Just to confirm, UuAs do not incur any change fee. It should purely be the difference of taxes/fees/charges between the two cabins.
I think that it should all be pretty clear by now, but just in case not:
If you take a cash ticket and upgrade it using Avios, this is a UuA and no change fee is payable.
If you take an Avios ticket and change it to a higher cabin by paying more Avios, that is a change and a change fee is payable. For this reason, I usually try to discourage people from referring to this kind of transaction as an "upgrade", even though in some senses it is.