In 1987, I was delivering a mobile tracking radar to the Air Force.
As part of the delivery, we were supposed to demonstrate the system.
Some cocky Air Force officer thought he’d pull a fast one on us by having a stealth fighter fly the test course instead of the regular plane.
He was amazed that our mobile system tracked the stealth plane through every maneuver.
I didn’t tell him until later that we were using the backup optical tracker, because the radar wasn’t seeing anything.
I'll bet the look on the officer's face would have been a hoot.