My days off it's running all day. I catch all kinds of stuff over the area we live. I didn't catch this one, but I periodically check the area it was
caught in.
but the SR71 wasn't black at that point but if other more gray or black aircraft are in the air that isnt controlled i would think it have their
transponders on to avoid a crash, even more so if it is something fast and stealthy where a normal aircraft might get in its way for what ever reason
They only need them on in controlled airspace, and an ADS-B can be programmed, so they can appear as whatever they want, and as soon as they're out of
controlled airspace, switch it off.