How many minutes past ETA will FSS consider an aircraft overdue?

The correct answer is that an aircraft is considered overdue by Flight Service Stations (FSS) if it is 30 minutes past its Estimated Time of Arrival (ETA). This timeframe is established as a safety measure to ensure that flight operations are monitored effectively. If an aircraft does not arrive within this window, it raises concerns that warrant further investigation, considering various factors like potential emergencies or adverse conditions that may have affected the flight.

This 30-minute criterion is based on common practices in aviation safety, emphasizing the need for timely communication and monitoring of aircraft. By setting this standard, FSS can take appropriate action if necessary, such as initiating search and rescue operations or contacting relevant authorities for assistance. The threshold is designed to balance the urgency of potential situations while allowing for realistic variances in flight operations.