Once the passengers are settled and the doors are closed, the duties of CAs depend upon the time available before the airliner leaves the ramp, taxies to the way, lines up and takes off. As an aircraft cannot be put into it has to be reverse, pushed back. The length of time is predictable and planned but if an airport is busy with traffic taking off and landing, there may be a delay. Although this time is used for passenger services, the essential job of the cabin crew is to check the safety procedures