While thinking of a trip from Seattle to Tokyo, I looked at the flight plans for UA 875 and DL 155, both nonstop. UA875 is a 772, while DL155 just upgraded from a 763 to 744.
Using both Great Circle Mapper and Flight Aware, it looks like UA875 sticks to the "optimal" route. The DL flight, however, goes quite a long ways farther north -- following the pacific coastline up through Alaska, and coming down through the middle of the Kamchatka Peninsula on the other side.
I couldn't for the life of me figure out why Delta would have a *much* longer flight plan and duration? I was hoping someone here could help explain.