Yes, you can plane-spot from inside the Terminals...especially in the brutal winters of Detroit. But other places to go are in roads and/or parking lots surrounding the runways for a great view. Some airports, like MIA & IAD, you can get real close. But my experience when I lived in Detroit was there isn't a good place to park that is real close. I don't know if they've changed that area in the last few years. Also, some airports have a specific observation deck, which if i remember correct DTW has.
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens