Aircraft move over the apron with as few engines running as possible, both after landing and before departure.
Pilots must taxi with as few engines as possible after landing and before departure. This helps us keep aircraft engine emissions as low as possible. This is only possible if it is technically and operationally safe. Sometimes it is not possible, for example due to regulations from the aircraft manufacturer or because it places too high a workload on pilots. Engines also need time to warm up before departure and cool down after landing.
The pilot always decides when to turn engines on or off. Together with airlines, we are investigating how we can taxi with one less engine more often. Many airlines also have their own programmes to encourage this.