What is the final event that marks the end of the flight duty period (FDP)?

The final event that marks the end of the flight duty period (FDP) is the final engine shutdown. This point is significant because the definition of the FDP encompasses both the maximum allowable duty time and the actual time flown. The end of an operational flight is determined when the engines are shut down, indicating that all airborne responsibilities have been completed. This event effectively transitions the status of the aircrew from operational readiness to off-duty.

Understanding the importance of this moment helps ensure compliance with regulatory requirements for crew rest and overall safety, as it contributes to preventing fatigue among aircrew members. The other options may relate to the flight but do not signify the conclusion of the duty period, thus highlighting the importance of engine shutdown as the definitive end to the FDP.