When does flight duty time officially end for a pilot?

The correct answer is that flight duty time officially ends when the engines are off. This point is crucial as it marks the transition from an active flying duty period to a post-flight status. Once the engines are shut down, the pilot is no longer responsible for the aircraft's operation, and this aligns with regulations concerning duty time, fatigue management, and rest requirements. Defining flight duty time in this manner ensures consistency and safety in operations, providing a clear boundary for crew members' responsibilities and ensuring they have adequate time to rest before their next duties.

Other choices, while they relate to the end of the flight or the pilots' responsibilities, do not accurately capture the point at which official flight duty time concludes according to aviation regulations. For instance, simply completing a landing does not account for post-landing duties or procedures that may still require the pilot's attention. Similarly, the crew debriefing involves discussions that take place after the flight, and exiting the aircraft may not signify the end of all responsibilities. Therefore, the shut-off of the engines is the definitive end of flight duty time as per regulatory standards.