Holding Stacks

When airports are busy, there can be a build up of aircraft waiting to land, and so aircraft can be placed in a holding stack.

A stack is a fixed circling pattern in which aircraft fly whilst they wait to land. The primary use of a stack is to delay an arriving aircraft due to aircraft congestion, sometimes due to poor weather conditions (e.g. snow clearing) or runway unavailability.

London Stansted Airport has two holding stacks; one called ‘LOREL’ which is located Northwest of the airport and the second, ‘ABBOT’ is located Northeast of the airport. The minimum altitude of aircraft in the stack is 7,000ft in the LOREL hold and 8,000ft in the ABBOT hold, and is set to keep noise on the ground as low as possible. The height of the holding stacks extends up to 14,000ft.

Air Traffic Control (ATC) must ensure there is a safe gap between each aircraft as they come in to land. To achieve this, aircraft will sometimes circle around in the stack until air traffic controllers are able to fit them into the landing pattern. Aircraft are required to carry extra fuel specifically for holding, should this become necessary. Any aircraft with an emergency would take priority and bypass the stack.

You can find out more by watching this video:

Aircraft leaving a stack

People living between the stack and the final approach may hear noise as the aircraft leaves the stack and makes their way to the final approach to London Stansted Airport. As there are no set heights or routes for arriving aircraft, once they have left the stack, aircraft are directed individually by ATC to ensure they are safely spaced for arrival. Therefore, they can legitimately go anywhere they are directed. ATC do this to ensure high levels of safety and efficiency.