Originally Posted by
af fp
If you use DL miles I think you will be better off buying a DL ticket, look carefully which fare classes are upgradeable with miles.
As far as I know (but I could be wrong, not too familiar with this) you cannot use DL miles to upgrade an AF ticket, or AF miles to upgrade a DL ticket.
It is possible but you need to have a full fare ticket (to make use of the Skyteam upgrade).
For other situations (except using SWU if you have them) there are not any options left.
Gajan