First, my standard is bone stock, no mods to the RC. Second, the location is wilderness, frozen lakes and rivers, spruce, pine and cottonwood trees. Nothing (that I am aware of) to interfere with the signal. OK, I went to the same place where I had previously gone 2.5 km to play with the camera settings while the sun was setting. I decided to go further in a WSW direction to have a look around. I was very surprised when it went past 3000 m with strong signals on the RC and Wi-Fi. I started getting weak transmission messages after 3200 m but the RC still had a few bars. As I got closer to 4000 m the RC was getting weaker but just a slight movement to aim the RC and I had 2 bars showing until it gave out and initiated RTH. The GO app crashed on the way back, here is the screenshot after restarting the app.