A similar rumor has NW adding a second SEA-NRT daily with an A330-200 since the demand for seats is high and, according to some regulars on that run, it's one of the few int'l routes that elites can actually expect a shot at an op-up on a semi-regular basis. (Then again, that same rumor held that the A332 used on the PDX-NRT run would be moved north to fill that second SEA-NRT slot but that had no basis in reality. So take this post FWIW.)

If there's any truth to this, I don't see UA surrendering any seats to its competition.