Warning: When I was there I "accidently" took some road leading to a fence near one of the cargo carrier's buildings. I remember seeing cargo containers from KL
being moved into one of the buildings. The view was the best I'd ever had while spotting at ANY airport. We were inches from moving aircraft. I'll never forget the VS
747 taxiing by us and then taking off. We only lasted about 2 minutes before security approached us and chased us away. Worth being caught by 3 police officers approaching us. As soon as we offered them ID
they new we were harmless Canadians and they told us just to leave.
I remember going somewhere else to see planes but I cant remember it. I am sure someone here from ORD
can help you find a nice place to spend an afternoon.