Originally Posted by
gvdIAD
If you want fast, you're probably going to need to take a cab. Expect the one-way fare to be about $60. If you're traveling on a weekday, one other option is the 5A Metrobus, which leaves 7th & D Sts, SW at 4:50 am, or Rosslyn at 5:02 am, arriving at IAD at 5:42 am...
5:42AM should be OK for a 7AM weekday flight, particularly if you have status (premium security line) and it's not Monday.