I booked ORD-FRA-JTR for a Friday in late May the day it opened. The ORD-FRA had 6 seats available in J. There was also a ton of saver awards ORD-BRU/ZRH/LHR but no real connections available. I've gone to Europe the same week almost every year for the last 10 and have noted UA always has decent availability to Europe around the time they open the schedule. Then they tend to pull that space back. As others have said....book while you can.