9,000 feet? That is impressive by any standard.

The farthest I have ever been with an RC plane was a 3.8 meter glider with a GPS logger in it. I reached a distance of 3,100 feet laterally and 2,800 feet vertically. That is a line of sight (slant) range of 4,177 feet. I was losing sight of it for half of every turn in the thermal I was in. I would need a telescope to see a plane 9,000 feet away from me!!