Range is limited by two things:
1) The height of the receiver antenna
2) The FCC
Obviously, if the receiver's antenna is higher up, it won't have as much issue with signal reflection, an issue with the early Spectrum 2.4 systems. This is also why, before we could bounce communications signals off satellites, ships had their radio antennas as high as possible, for longer range. They didn't know, back in those days, that the low frequency signals they were sending could reach beyond the horizon, unlike the high frequency signals we use today.
The FCC is the real limiting factor in radio ranges. The law, as presently written, only allows an R/C transmitter to broadcast using .5 watt. This effectively limits your range to around 750-1000 yards, at best. While aircraft systems can reach a bit further, it's only due to the fact that the transmitted signal isn't attenuated by the ground or water. I would consider it more likely to reach ranges of not much more than 500 yards, with reliable reception