Originally Posted by
bpk6h
As this is a mixed class (Y on EI/PY on SQ) /mixed airline (EI/SQ) booking, SQ's systems will be challenged. While SQ can sell the ticket upfront (somewhat impressive given SQ's IT), their upgrade engine is clearly using an alternative source to calculate fares.
I think this may have more to do with it: the repricing would likely be based on the whole itinerary, not only the AMS-SIN sector. This means the upgraded price would be based on a theoretical fare that would include DUB-AMS in business, and that might well map into a much higher fare bucket than what you could buy AMS-SIN for in business outright.
That’s only one possible explanation, of course there are others…