Thank you, both.
The UA website seems very straightforward.
I started by searching for flights from Washington, DC to Barcelona around July 6 and found plenty to choose from beginning July 9.
Unfortunately, when I looked for a return flight from Paris to DC, there seems to be nothing available until mid-August. (If I depart the US on July 9, I'd like to depart from Paris on July 18.)
Am I just out of luck because I'm trying to travel in the peak season? (Surprisingly, going over there seems to be plenty of space at the "low season" rate.)
Ron