Skycircl.es Advisory Circular
The Advisory Circular is a network of twitter bots posting in real-time whenever they detect aircraft flying in circles over cities around the world, including Los Angeles, Baltimore, Portland, Minneapolis, and London. Because they use an uncensored source of data, the bots also record police, FBI, DHS, DEA, CBP, and military aircraft. They look for circles because it means an aircraft is doing something instead of going somewhere. If you’ve ever asked “what is that helicopter/plane?” there’s a good chance these bots can answer your question—even if it’s an advanced military surveillance plane.