radar is a system that sends a radio beam out and hits an object and could be a cloud or a bird or obviously an airplane. that signal is returned back. from that the radar controller can see the blip on the screen. with this airplane we don't know what altitude it was at when it made the turn around. we are not sure if it flies back to radio cover annage. in order for them to see the airplane, it would have to fly back. the tron responder was not transmitting. this was an extra packet. they are seeing altitude air speed heading and identified the airplane. it's a specific code. that goes along with the radar blip. you are missing the packets. all you will see if it flies back is just a little blip and how long were they in radar coverage. you need many, many sweeps to be able to identify the airplane.