What is a significant requirement for flight reporting in a non-radar environment?

In a non-radar environment, one significant requirement for flight reporting is the obligation to report any changes in estimated time of arrival (ETA) by more than three minutes. This is crucial for air traffic control (ATC) to manage air traffic safely and efficiently, especially when they are relying on pilots' reports to maintain situational awareness and coordinate incoming and outgoing traffic.

Timely and accurate communication of ETA helps ATC anticipate aircraft positions and facilitate appropriate spacing, which is essential in environments where radar is not used. Such updates ensure that safety is maintained and that air traffic is organized effectively, especially during arrival procedures or when transitioning between different airspaces.

The other factors, while important in flight operations, do not carry the same level of urgency in non-radar communications. For instance, while visibility reductions and altimeter setting changes are essential for safe flying and reporting, they are not specifically mandated as significant requirements for reporting in a non-radar context. Weather updates at checkpoints are also relevant but do not have the same direct impact on traffic management as a significant change in ETA.