I haven't yet flown IAD-FRA yet, but as a 1K for about five years now, I've only failed to upgrade once (about three years ago from SFO-NRT). Its been my experience that many times, my upgrade requests won't clear until I'm at the gate. I frequently fly to Asia, so perhaps UA doesn't release upgrade space until the last minute. Anyway, I've learned not to sweat it if my upgrades don't clear until I'm at the airport. I feel badly for the 1P's and 2P's that are milling about, hoping their upgrade requests will clear, which are almost always in vain.