United is currently the largest user of the 777 and therefore has the largest number of doemstic 777 flights. SEA/DEN DEN/IAD ORD/IAD LAX/DEN LAX/ORD SFO/ORD are some of the routes that I know of where you can fly on a UA 777. Expect to find more and more AA 777 on domestic routes as their 777 fleet grows.