When is it required to file a flight plan or itinerary?

Filing a flight plan or itinerary is essential for ensuring safety and coordination in aviation operations. The requirement to file is especially critical for flights that are conducted beyond 25 nautical miles from the departure aerodrome. This distance is significant as it indicates that the aircraft is entering areas where it may require additional air traffic control support and coordination due to increased air traffic complexity. By filing a flight plan, pilots communicate their intended route, altitude, and estimated times of arrival, which enhances situational awareness for air traffic controllers and increases the safety of the flight.

The other options present conditions that may not universally require a flight plan. While some operations, such as night flying or operations over populated areas, may necessitate additional caution or measures, they do not specifically trigger the mandatory requirement to file a flight plan. The 25 nautical mile threshold serves as a clear legal and operational guideline for when a flight plan is obligatory, ensuring that all flights venture into more controlled airspace have proper documentation and monitoring.