@Spitfire76 I use the cree ones, we tested over 3 miles. One easy test is to look out a plane window, most people have a 40-100 watt bulb on their front porch, you can see it from jet liners flight levels. I bought the white and stick it right on top.
https://mdpair.com/shop/strobon-cree-standalone-battery-operated-3-mile-visibility-strobe-light-drones-like-phantom-inspire-mavic/
I'll have a video of it soon.