Stealthy no more? A German radar vendor says it tracked the F-35 jet in 2018 — from a pony farm

In the illustrious history of the F-35 fighter jet, add a pony farm outside Berlin as the place where one company claims the plane’s stealth cover was blown.
The story that follows is a snapshot in the cat-and-mouse game between combat aircraft — designed to be undetectable by radar — and sensor makers seeking to undo that advantage. In the case of the F-35, the promise of invisibility to radar is so pronounced that it has colored much of the jet's employment doctrine, lending an air of invincibility to the weapon: The enemy never saw it coming.
But technology leaps only last so long, and Russia and China are known to be working on technology aimed at nixing whatever leg up NATO countries have tried to build for themselves.
Now, German radar-maker Hensoldt claims to have tracked two F-35s for 150 kilometers following the 2018 Berlin Air Show in Germany in late April of that year. The company’s passive radar system, named TwInvis, is but one of an emerging generation of sensors and processors so sensitive and powerful that it promises to find previously undetectable activities in a given airspace.