What method can be used to amend the Estimated Time of Arrival (ETA) when conditions change?

The method of applying the new ground speed to the distance remaining is the most effective way to amend the Estimated Time of Arrival (ETA) when conditions change. This approach allows for a direct recalculation of the ETA based on the most current and relevant data—specifically, the aircraft's current ground speed and the distance that still needs to be traveled.

As ground speed can be affected by various factors such as wind, aircraft weight, and air traffic, using this speed provides a realistic assessment of travel time. By dividing the remaining distance by the new ground speed, you can derive an updated ETA that reflects the current conditions.

In contrast, recomputing flight distance may not always consider the dynamic changes affecting the flight path, while contacting ATC for a new ETA is useful for coordination but does not directly amend your calculations based on flight conditions. Adjusting the route based on weather forecasts can also be important for safety and efficiency, but it does not provide a straightforward calculation for the ETA unless it results in a specific new distance or speed to evaluate.