Originally Posted by
christep
True for money, but it is possible to upgrade individual xONEn sectors using miles. I've done this with AsiaMiles in the past using a roundtrip upgrade where the underlying sectors were actually on two separate DONE3 tickets.
Upgrading flights on oneworld tickets are only possible with L fares on flights with premium economy with a per sector surcharge, or within the rules of a frequent flyer program.
ie, as a QFF member, I can use my QF points to upgrade QF coded, QF operated flights on an xONEx.