Yesterday we flew Chicago to Frankfurt UA944 with shockingly light load. I didn't count it myself, but the flight attendant mentioned they only had 100 people checked in (a 777 with about 270 seats) so "feel free to stretch out".
Half of the E+ were people grabbing three seats each. Business had one empty seat only, not sure about First. I've taken one of the ORD-FRA or ORD-MUC trips about once a month, and they tend to be very full. Definitely a decent way to travel in coach even if it means not taking the most direct route. Is it the early afternoon departure, slow season, economy, or just an exception ...?
For now, I'd say that it is a rare occurrence, but just wait until AA starts going head-to-head with UA using aircrafts with the new AA products and UA's load factors will fall.