I'm guessing this is just an optical illusion, but who knows. I've lived near O'Hare Airport all my life, and I can tell what airplanes look like day or night. While driving Westbound as a passenger tonight, I saw out of my right window looking NE something that made me utter out loud "what the hell?" I saw four white lights in a perfect square with a red strobe near the rear section of the craft. The craft turned, and then it looked like three lights close together. I'm guessing it may have still been a commercial jet, but I've never seen an angle which could make a jet appear as four lights in a perfect square. I believe it was traveling Eastbound or slightly ENE, and if it was a regular jet, my guess at the altitude puts it at 2-3,000'. I have my doubts it's anything unusual, and I'm sure there's a logical explanation. Perhaps the pilot activated a rarely used light by accident, giving the appearance of four lights. My mother was also a passenger in the car, and saw it too, asking if I saw the "double decker plane." I asked if she saw a square shape of lights too, and she did. We passed by some trees and I lost visual contact. Also, I didn't notice any directional lights (red and green) on the wingtips that planes usually carry. Weather conditions, cold, about 28F (in dash thermometer) and overcast, with a fairly high ceiling.