The flight schedule refers to the time when cabin door is closed for take-off, and not that of the actual departure.
　　　
A flight can be cancelled or delayed because of weather factors, mechanic trouble, navigational factors, delayed arrival of incoming flight, flight schedule adjustment, and other factors such as unscheduled inspection/maintenance by aircraft manufacturer, exercises, security check, computer crash, ground operation, runway, and facilities. Passenger may request seating on a similar destination flight or booking with another airline if after completion of check-in procedures in time (30 minutes before departure time for domestic flight), and seat assignment.