Originally Posted by
mgcsinc
Unless they've added it to the mid-field immigration area, you'd have to head to the IAD-is-your-final-destination route, and then go through TSA in the main terminal. Wouldn't work if you had a checked bag.
There is still no PreCheck at the midfield FIS, and the security line there can be horrendous at peak times. The route described above, despite additional travel time across the airport, is usually advantageous.