Where should a cruise clearance with no crossing restriction be issued?

A cruise clearance with no crossing restriction is typically issued at airports where no Instrument Approach Procedure (IAP) is published. This is important because the absence of an IAP means there are no established procedures for instrument approaches, which could be critical for aircraft operations during poor weather conditions.

In these scenarios, issuing a cruise clearance allows aircraft to maintain an appropriate altitude and ensure a safe level of separation from terrain and other traffic, while the pilots can follow their own navigation decisions without relying on standard IAPs that may not exist.

In contrast, issuing cruise clearances at airports with published IAPs could lead to complications, as the pilots might be expected to follow specific standards and procedures that align with those approaches. Similarly, issuing such clearances only in controlled airspace or at any point during flight may not account for the operational limitations that arise when navigating in areas without established procedures. Thus, the answer reflects considerations of safety, operational procedure, and regulatory compliance.