F-35 and F-117 Spotted Flying with Mysterious Mirror-Like Skin

When they want to know what an aircraft looks like without the radar absorbing foams and paints they do that during the testing phase, typically on a prototype that simply hasn't had the fancy stuff applied. Anything done to increase radar signature is typically the aircraft equivalent of the reflective belt.

I think the author's hypothesis about IR is far more likely and provides much more justification for why and old type (that they've presumably long since had radar information for) would be tested alongside a newer type.

> Probably a stupid question, but my first thought was, "doesn't making it more detectable defeat the purpose?"

Maybe you don't want your stealth aircraft to be stealthy during peacetime, to avoid giving your adversaries the possibility to get their hands on some valuable training data. For example, if you are China or Russia, wouldn't you place some agents with some antennas around the US Air Force training bases and compare the radio reception with the visual sightings? If the radio reception is not the same you'd see during wartime, all this exercise is futile.

More accurately, to make it more noticeable to sensors or alter it's signature (eg. the sine waves on the wings probably aren't just for looks).