If approach control service is not provided, how many miles from the destination airport should an altimeter setting be issued?

When approach control service is not provided, the recommended practice is to issue an altimeter setting at least 50 miles from the destination airport. This ensures that pilots have sufficient time to adjust their altimeters appropriately as they approach the airport, which is critical for maintaining accurate altitude during the descent and for safe landings. Providing the altimeter setting well in advance helps mitigate the risks associated with changing altimeter readings that can occur due to variations in atmospheric pressure, thus enhancing safety in the approach phase of flight.