We prefer to eat at the airport before we fly, rather than carrying food onboard.
The good news is that there are a lot of good choices in the American Airlines terminal at Chicago-O'Hare. We usually get to O'Hare about two hours before departure time. After check-in and security, we usually still have over 60 minutes before boarding time.
There are two table service restaurants just inside the security checkpoint -- Wolfgang Puck's and Chili's. Then, there's a big food court further in the gate area. And there are bunch of fast food places throughout the concourses, such as McDonald's and Great American Bagel.