Seems like the Prez was returning home (south side of Chicago) for the holiday weekend. I thought he was to make a trip Friday afternoon to Louisiana area to look at oil disaster. Perhaps he was returning to the ORD, then Marine One to Soldier Field to meet motorcade, then "home". If he stays in the Chicago area for the weekend, I would not be surprised if he took in the Blackhawks-Flyers Stanley Cup hockey game(s) on Saturday and Monday. Not sure if that is the activity you heard, but fighters in the air while the prez is in town wouldn't be too much of a stretch. You might hear/see a nice air show this weekend.