How soon should you take action to obtain a position report affecting separation?

Taking action to obtain a position report affecting separation at 5 minutes after the estimated time over the fix is correct because this timeframe allows for effective monitoring and management of air traffic in relation to separation standards. When aircraft are navigating toward a specific fix, understanding their position after this duration can provide valuable information regarding their trajectory and altitude.

This action is crucial, particularly when considering separation requirements and ensuring safety in controlled airspace. By acting at this specific interval, controllers can verify that aircraft are on their planned routes, thus maintaining the required separation and preventing potential conflicts. Position reports at this point provide essential updates that can influence decision-making, routing adjustments, or altitude changes.

The other options either focus on times that are too early or too late for effective management of air traffic in this context or refer to conditions unrelated to immediate separation needs. Taking action right after take-off could be premature as the aircraft may still be climbing or still below certain altitudes. Reporting at an aircraft's initial altitude is also not necessarily timely enough to assess separation. Finally, waiting 10 minutes after departure may exceed the necessary timeframe to check for proper separation, especially in busy airspace.