Originally Posted by
FliesWay2Much
On a relative scale, this time of day is absolutely horrible at Dulles, but, there's nothing you can do about that because of the European destination. I would get there at least two hours ahead regardless of screening. At that time of day, people are backed up just to get down the escalator. You'll also have to account for additional time to drop off your checked luggage and even more time if you want to stay there in case the screeners open it up.
I was just there earlier in the week. If you go through the security entrance closest to the parking garage, there are no NoS's in that area. I can't vouch for the security chackpoint right behind the United counters. I know there is one in the small "Black Diamond" lane downstairs near baggage claim. So, avoid that line at all costs. If you have an upgrade, you can go through the shorter line once you make it downstairs.
As of 2 weeks ago, the only NoS at IAD was at the Black Diamond lane. If you are checking baggage, I would recommend 3 hours - FW2M is right, you are going to be experiencing Dulles at the worst time possible. Unless you have status with UA, I would also avoid the UA end, because it is usually the more crowded security location.