Duty Period is defined as:
a. Any time a crew member is required to undertake activity on behalf of the airline is considered as duty time. This includes flying, dead-heading, admin duty, standby, training, etc.
b. Calculated from the moment a crew member reports for duty and ends once they are free from all work-related activities.
c. Calculated from the moment the aircraft moves under its own power for the purpose of flight until it comes to a full stop and the engines are shut down; essentially off-blocks to on-blocks time.
d. All of the above