I know for a fact that DL operates 2 daily 777 flights to Paris as well as 2 777 flights to London. I just flew ATL-LGW and back last week on DL 777's. As we were in the busines elite lounge waiting for our flight, the 6PM Paris flight was boarded and departed from the gate right in front of the window of the lounge. It was N864DA, which is the airplane painted for the 2002 Olympics.
Oddly enough, that was the same airplane which flew us back from LGW to ATL a week later.
Art at ISP