Flight Leonardo da Vinci–Fiumicino Airport departs from Rome Leonardo da Vinci–Fiumicino Airport at 15:40 and arrives at Washington Dulles International Airport at 19:50.
The flighttime is about 10h 10m. The distance travelled ("as the bird flies"): 9976 Km. So the average speed is roughly 981 Km.
There is an 6 hour time difference between Rome and Washington