What is one criteria that must be reported as a change in flying conditions?

Reporting unexpected holding as a change in flying conditions is essential because it directly impacts flight safety and operational efficiency. Holding patterns are often a result of unforeseen circumstances such as weather changes, airspace congestion, or emergencies, and can affect fuel consumption, passenger comfort, and adherence to schedule. By acknowledging unexpected holding as a change in flying conditions, flight crews can ensure that all relevant parties remain informed, allowing for better communication and decision-making regarding flight management.

In contrast, while flight route changes, flight delays, and new crew assignments may also be important updates, they do not necessarily indicate a shift in the immediate flying conditions that are crucial for safe flying. Flight route changes might be planned and communicated adequately before departure, flight delays involve scheduling but not changes to the conditions in which the aircraft operates, and new crew assignments typically pertain to staffing rather than flight environment. Therefore, unexpected holding is distinct and critical to report as it signifies a direct alteration in the operational situation faced by the flight crew.