There are a couple of the TPAS Aircraft detectors on e-bay right now. These units work very well if you live or travel threw aircraft enforcement areas. The best part about these units is you can set a window IE: Only aircraft less than 1500' up and 1.5miles or less will get a warning from the Trafficscope. The other thing I do not like it the alert is a soft woman's voice that is speaking airplane lingo and requires an amplified speaker to hear what is being said. There was one that closed about a week ago and went for $115. These units cost about $500+ when they were new. I have ran my unit quite a bit threw NW Ohio and Indiana and eastern Illinois. It has alerted most of the time when aircraft are in the window setting. After much looking I usually find the plane or helicopter close by. What I have not found is a active enforcement zone in effect. I do not think Indiana does aircraft enforcement but they do have the White lines painted in a number of locations.