How far you can track an AirTag will depend on the method you're using to track it. If you're using a Bluetooth connection, then the Apple AirTag tracker range will be only as much as the Bluetooth, which is about 15 to 30 feet, depending.  Now, the tracking range will be much farther if you're using the Find My app on iPhone or other iOS devices. You can track it around the world as long as it's pinging off of a service tower, much like you can track your friends' and families' phones wherever they are in the world.