Under what condition is the forward departure time or subsequent strip posting time not required?

The condition where the forward departure time or subsequent strip posting time is not required is when the assumed departure time is within three minutes of the actual departure time. This is because if an aircraft is scheduled to depart, and there is minimal variance from the actual departure time, the operational impact is minimal. Controllers can rely on the timely adjustments and avoid unnecessary updates to the departure information as the flight is about to commence.

This close alignment indicates that the flight's movements are very predictable in this timeframe, simplifying workflow and allowing for a smoother operational process for air traffic control. Since the actual departure is so close to the assumed departure, there is less need for additional administrative steps or updates that might otherwise disrupt the flow of information.

In contrast, if an aircraft has not yet taken off, or if the flight plan has not been filed, or if a destination change is made, those situations create a need for more detailed tracking and updates to ensure safe and efficient management of air traffic. Each of these factors could fundamentally alter flight operations and necessitate updates for clarity and safety, whereas being within a three-minute window indicates continuity and reliability in that short time frame.