It's a bit more what they call "line of sight". You need to be able to see the plane. If it gets behind something or even someone it reduces the signal strength somewhat. The higher the frequency the more these factors come into play. Normal standing on the flightline with others should be fine though. They are considered "full range" systems with the exception of units like the DX6 which the mfg rates as a park flyer radio due to low power and single RX.