The range depends upon:
The position and the power of the transmitter.
If the 'person' transmitting is the pilot in a 'plane at, say, 10,000 feet, you might well pick his transmission up many miles away.
If the 'person' transmitting is an air traffic controller at an airport, it will depend on numerous things... location and size/importance of the airfield, geographical features: hills/buildings etc.
And it goes without saying...
You are not allowed to listen in to ANY radio transmissions unless authorised to do so. I'm sure someone will be along to point you in the direction of that rule...................