What marks the start of a flight duty period (FDP)?

The start of a flight duty period (FDP) is marked by the moment a flight crew member reports for official duty. This definition is crucial in aviation regulation and safety management because it delineates the period during which flight crew members are considered to be on duty, which impacts scheduling, rest periods, and overall flight safety.

When a crew member reports for official duty, it indicates that they are ready to engage in pre-flight activities, which can include briefings, equipment checks, and preparation for the flight. This reporting time initiates the clock on the FDP, and from this point, regulations typically dictate how long they can operate before requiring a rest period.

Understanding this concept helps ensure that flight crews are adequately rested and prepared, thereby mitigating the risk of fatigue-related incidents during flight operations. Other choices, such as aircraft engine startup or taking off, occur after the flight duty period has commenced and should not be confused with the official start time of the duty period.