Originally Posted by SEA_Tigger

Please note that the 777XC and 777XI aircraft have identical seatmaps now. As IFLYUA noted, this route is served by XI aircraft, usually, and on occasion an XP.

With a maximum range of 5,210nm (per Boeing's site), a 777XC is right on the bubble at doing SEA-NRT. While it probably could do it, it might not be able to fly fully-loaded, especially when facing headwinds SEA-NRT (B747-437B has a great handle on aircraft ranges and loadouts, so he might be able to offer a definitive answer).