Originally Posted by Axey
SQ accepts upgrades from NH and LH through the same program. It's UA specifically. I'm not surprised, to be honest.
My guess is that SQ realizes that UA miles are a throughly degraded currency, with the constant flow of double, triple, quadruple and othe bonus miles for doing little more than punching your MP number into a website.
Airlines like ANA, LOT, Thai and TAP are probably using this to try to draw UA customers to their service offerings as they are a bit lesser-known quantities, whereas the immediate reaction on this board indicates that SQ has no such issue.