It should be noted this was line of sight, 10-50 watt transmitters on omni directional antennas, 4200' above my location, with a mobile VHF/UHF/800MHz scanner antenna. YMMV
I think the greatest distance I have gotten a close call hit from was about two miles (approx 3.2 Km). It was a construction crew doing some emergency repairs on a major expressway interchange. I don't know if it was a handheld unit or a higher powered mobile in a vehicle, but the reception was crystal clear for the 45 minutes or so I was receiving it.
The range depends all of how much signals you have at other frequencies. Using a FM trap filter while doing close call in airband 118-137MHz will easily get over 10km ranges depending of hight of aircraft.