I worked in the air-force as ground-crew servicing F-16 for a year. Every now and then they would exercise gun target-practice by having one jet tow a red "sail" (I think it was called a "taxan"). The towing-line was several hundred feets long, and the towing jet would fly in a large circle. The practice always intrigued me, and seemed very low-tech compared to some of the other stuff in the domain. Don't know if that was what you saw but - they did not fire missiles at the target how ever, and certainly not over populated area. They always flew out over the North-sea.