What is the primary purpose of a cruise clearance?

The primary purpose of a cruise clearance is to provide Search and Rescue (SAR) protection until the IFR flight plan is canceled or closed. When a flight is operating under IFR, obtaining a cruise clearance not only allows the pilot to navigate the airspace but also ensures that they remain covered by SAR services. This is essential because should there be any unforeseen issues during the flight, such as an emergency or a loss of communication, ATC and rescue services will be aware of the flight's last known intentions and route.

While navigation without ATC communication may be a result of a cruise clearance, it is not the primary intent; rather, the focus is on ensuring safety and readiness for any potential rescues. Altimeter settings are important for compliance, but they do not relate directly to the purpose of a cruise clearance. Lastly, training maneuvers in controlled airspace have their own set of regulations and clearances, separate from a standard cruise clearance. The SAR coverage during the flight's duration under IFR is the key aspect that defines the primary purpose of a cruise clearance.