Originally Posted by Pyrite
Hmm. Thanks for the input. The good news is that I will have only carry on and may be dropped off at departures. The other option is staying overnight nearby and calling for a taxi. It seems most of the hotels do not start their shuttle service until 5:00 am and it sounds like that would be cutting things a bit too close. My flight is to ORD so I suspect that the C/D terminal will be in my future.
If you are dropped off then 45 min to 1 hr should be fine. (The former if my assumption about it being quiet at that hour is correct.) If the hotel shuttle actually departs reliably at 05:00 then no problem. If you stay at the Marriott then you can walk across the street and enter garage 1 and walk through the tunnel or catch a parking garage shuttle.
I have never arrived at IAD more than an hour before departure and do just fine.