From observation, the domestic airlines operating 777's, CO,AA, UA, and DL, aircraft for the most part fly long range international routes or to Hawaii.
Sometimes you will see them operating hub to hub, EWR-IAH, ORD-DEN, DEN-LAX, DEN-SFO, DTW-ATL, MIA-LAX, MIA-DFW,JFK-MIA, usually for aircraft positioning or the aircraft is avaliable to operate on a route where the capacity is needed.