Any time you will be more than _____ minutes late, you should update your ETA with FSS.

The correct answer is the limit set by protocol for updating your Estimated Time of Arrival (ETA) with Flight Service Stations (FSS). Updating your ETA is a crucial aspect of maintaining communication with relevant aviation authorities, ensuring safety and situational awareness.

When you are more than 15 minutes late, it highlights a potential issue or change in your flight plan that the FSS needs to be aware of. This allows them to assist in any necessary adjustments or assist in locating aircraft that may be in distress. By adhering to this timeframe, you ensure that the information remains current, thereby promoting safety both for the flight in question and for air traffic control operations at large.

The other timeframes listed—10, 20, and 30 minutes—do not align with the established guidelines, which dictate that 15 minutes is the appropriate threshold to activate an update. This balance ensures efficiency without overburdening the system with unnecessary updates for small delays.