Originally Posted by
wayfarer613
Alright, just passed through IAD, and it was as I suspected. A-->C runs pretty much all day; A-->D runs during peak connecting hours - splattered all through the day. You're supposed to take the C shuttle when the D shuttle isn't running.
Hope this helps.
Thanks for checking; this confirms what I remember (that D to A only operates during certain hours). I have a two hour connect, so that should give me ample time to walk from D to C and hit one of the RCC along the way.