They have been running 744's on this route lately (a 7:54 am flight out of SFO and back from IAD at 5:30).

One word of caution--when I was booking a flight recently I noticed the seating chart in both F and C showed some "phantom" seats (seats that I know couldn't possibly exist on this plane).

That said, I recall seeing that they were switching this flight to a 3 class 777 later this summer, so I would probably call United to see what is up so you don't have any surprises when you get on board.

Tim