I've been living in the north shore for over 11 years, in particular, South Evanston. As long as I could recall, and when I was awake past midnight I almost always heard a plane pass overhead. I'm certainly not an expert but assume it was a Cessna. The typical routine was flying on weeknights between midnight and 2am. Knowing that Palwaukee airport is not too far away it probably either flew out, landed or did both there. My belief is that it was some pilot who needed to log in a certain amount of mileage on a monthly basis, and did so enjoyably during the wee hours of the morning well after work. If one of your investigators can find out what the story is it would certainly resolve my curiosity! Keep up the great work. Excellent radio segment and thanks!