Notes about the AT5 file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The AT5 file type is primarily associated with 'Lowrance' by Lowrance. The Lowrance AirMap product family provides hardware with flight-based features to give you the information you need to be safe. This is a form of map file for the device.