When is a pilot required to carry a flight manual or operating handbook?

A pilot is required to carry a flight manual or operating handbook at all times when flying an aircraft, making this the correct answer. The flight manual contains essential information about the aircraft's operating specifications, limitations, and emergency procedures, which are crucial for safe flight operations. This requirement applies universally across different types of flights, ensuring that pilots have access to critical information regardless of the nature of the flight, whether it is training, commercial, or private.

In addition, having access to the manual enhances situational awareness and decision-making ability, especially in emergencies. The other choices suggest that the requirement to carry the manual only applies in specific situations like commercial flights, training flights, or night flights, which is misleading since safety standards dictate that pilots must have the operating handbook on board for every flight to ensure they can respond appropriately in all scenarios.