What two actions must happen three hours after door closure?

The correct answer highlights two critical actions that must take place after the aircraft doors have closed for at least three hours, specifically indicating that the flight must either have taken off (wheels up) or the main cabin door (MCD) must be opened.

This is essential in the context of flight operations because once the doors are closed, the aircraft is in a state of readiness for departure. The phrase "wheels up" signifies that the aircraft has successfully taken off, thus moving toward its operational status. Alternatively, if the doors are opened, it indicates that the aircraft is not in a flight operation phase, which may align with emergency situations or operational delays.

Maintaining an understanding of these actions is vital for crew coordination and flight safety, ensuring that all necessary procedures are followed for a smooth operation after the doors have been secured.

In contrast, other choices don't accurately represent critical operational thresholds three hours post door closure. For instance, passenger seating in the cabin is typically required prior to this time but isn't specific to the three-hour mark, nor are actions related to fueling or maintenance checks which indicate behind-the-scenes operational concerns rather than direct flight readiness or departure status.