Annandaler is right that there will be a subway, but I wouldn't count on it anytime soon. I believe that someone mentioned 2009 as a target when I was last on one of the moon buggies (though my memory could be wrong--or they could be wrong). IAD is not a fun place and is difficult to get around (though thanks to Ozstamp's recommendation some time ago, I now go to the security line by Aeroflot, which is far less crowded than the main one by UA ). But it does service UA (and is the closest airport to my house!).