This Is The Info From Apple About The Range
"You can locate an AirTag that's thousands of miles away or even internationally, providing it is within Bluetooth range of an iPhone. AirTags do not have a defined range. You can track one thousands of miles away and even internationally overseas.
An AirTag uses Bluetooth to connect to an iPhone during the initial setup process, and an iPhone needs to be within a range of 33 feet to connect to any Bluetooth device. Therefore, and regardless of the actual range of an AirTag, the operating distance is 10 meters.
If the AirTag is out of reach of the Find My network, only it's last known location will be shown in the Find My app. If it happens to connect to an Apple device later, the location will be updated.
In other words, if you leave an AirTag in a coffee shop on the other side of the world, you should be able to locate it. However, if you lose an AirTag in a remote-but-nearby place like the woods behind your house, you won't be able to find it unless someone with an Apple device walks into its Bluetooth range."