This may not help you for close-ups of planes, but try atleast this, you've gotta try it. Take a hotel shuttle, or just drive, to the Hyatt Regency Hotel located only 1 mile east of ORD. Go all the way to the top floor, there is a revolving restaurant there with a spectacular view of ORD and downtown Chicago on the other side. The best time to go up there is at night, because of all the lights. And, depending on the landing patterns, you'll see aircraft flying only a few hundred feet past the hotel on their final approaches. Sometimes their altitude is level with the hotel's top floor, you've gotta try it... Oh yeah, the food is great as well.