Originally Posted by QRC3288

Actually, there is more just to be clear as to why this isn't possible.

You cannot upgrade any Y sub-fare class to J on a route with PEY, which is basically every medium and long-haul route. So the best you could do is Y->PEY.

But even if you could, only Y, B, H, K and M are eligible for upgrade using Asia Miles.

S is a heavily discounted ticket. As part of the "deal" for selling you this type of ticket, they're *usually* nonrefundable. This means even upgrading it to a higher sub-fare class is not possible.