When does the Captain assume command of the crew?

The Captain assumes command of the crew at the time of reporting for duty. This is a critical point in aviation operations as it signifies the transition of authority and responsibility from the airline management to the Captain. Once the Captain reports for duty, they are responsible for all operations involving the crew and the aircraft, which includes ensuring that all safety protocols are followed, the crew is properly briefed, and the aircraft is ready for flight.

This means that from the moment the Captain steps into their role, they take on the full responsibility for leading the crew and making crucial decisions regarding the flight, which includes overseeing pre-flight checks, preparing the crew for what lies ahead, and being accountable for the safety of everyone on board.

The timing of this command is significant, as it establishes the chain of authority well before takeoff and allows the Captain to start planning for the flight and managing the crew's dynamics.