Was crossing rt 23 bridge and was halfway across the bridge northbound when I saw the large gray colored object very slowly headed west as if it was following along the north side of interstate 80. The object was about two miles west of Walmart. I watched the object for 45 sec but due to its low altitude and city buildings I lost sight to it. The object was battleship gray and I did not see windows or lights. It's flight pattern was straight. I add that I have served in the military and have seen many types of aircraft and have never seen an object like this before that exhibited these flight characteristics. It was not a Blackhawk, Chinook, air ambulance or plane from the nearby skydive Chicago. The object seemed to be bigger.