For an aircraft without a flight plan, how long must it be reported overdue at the destination before it is considered overdue?

For an aircraft without a flight plan, it is considered overdue at its destination after a period of 1 hour. This time frame is established to ensure adequate safety measures are in place, allowing for a significant margin to account for potential delays or diversion due to weather, mechanical issues, or other unforeseen circumstances.

The 1-hour mark provides air traffic control and search and rescue operations a practical time frame to assess an aircraft's status before initiating formal overdue procedures, ensuring that all possible investigative actions are conducted efficiently. Understanding this time frame is essential for maintaining effective and safe operations in air traffic management.