Originally Posted by
minhaoxue
Obviously it is to get into the same Terminal as their One World partners.
Partners? The only OW airline in T1 is AA. I don't think it makes any sense at all to move just to be next to AA at SFO. The two airline don't have complementary networks from SFO; rather, they compete on several routes.
My guess would be that SFO offered them a deal. UA probably wants more real estate in T2.