So, I live in NJ and regularly fly about 5,000 feet away before interference starts to creep in. To get farther, I need to exceed the 400 ft limit. I was in Phoenix this week and took the bird for a few spins. Got out to 11,000 feet (personal best) easily at altitudes below the limit. I only use a windsurfer and am pleased with these numbers. This leads me to believe range is more affected by interference from the ground than anything else. Densely populated areas = limited range, period. ****, these things are fun!