Flight Tacoma International Airport departs from Seattle Tacoma International Airport at 07:00 and arrives at Washington Dulles International Airport at 20:45.The flight has a short stop at Houston.
The flighttime is about 10h 45m. The distance travelled ("as the bird flies"): 4975 Km. So the average speed is roughly 463 Km.
There is an 3 hour time difference between Seattle and Washington