In what scenario is it unnecessary to assign the highest available altitude?

Assigning the highest available altitude is important in many scenarios to ensure safe separation between aircraft and to adhere to air traffic management procedures. However, in the absence of air traffic restrictions, it becomes unnecessary to assign the highest altitude. When there are no restrictions, pilots have more flexibility in altitude selection as they are not constrained by the need for maximum separation from other air traffic. This allows for operational efficiency and may enable aircraft to achieve their preferred altitudes that align with their flight plans, fuel efficiency requirements, or performance capabilities.

In contrast, scenarios like a non-precision approach, occupied altitudes by another aircraft, or departures from smaller airports typically involve specific operational considerations or constraints that necessitate attention to altitude assignments for safety and traffic management. Thus, the absence of traffic restrictions is the key factor that allows for more flexibility in altitude assignments without the need to default to the highest available altitude.