• Major international airports are complex operations, potentially with multiple runways and terminals linked by miles of taxiways.

    The movements of aircraft (airborne and on the ground) are controlled by air traffic control from a control tower. While at some airports controllers will have ground radar to assist them, most direction is done by sight. This includes making sure that ground vehicles are safely separated from aircraft.

    Pilots have a chart of each aerodrome showing details of both the runways and the taxiways.

    Did you know? The wind determines direction of take-off and landing, as aircraft must fly into the wind during these phases of flight. Air traffic controllers will bear this in mind when choosing the most suitable runway.

    Flight management and air traffic control

    Before taking off every airliner has to file a flight plan with air traffic control. The flight plan describes the route to their destination and the timings of the flight. These details are entered into a central European system and an air traffic control ‘slot’ for the flight is allocated. This system ensures that all air traffic controllers along the route are aware of the flight and have the capacity to handle it at the time it’s due to be in their airspace.

    If an aircraft misses its slot, for example if it has a maintenance issue or a passenger is late, then this clearance will probably need to be re-submitted and a new time approved.

    At the end of the journey, when approaching a busy major airport, air traffic control may put aircraft into a holding pattern or ‘stack’ so that the arrivals can be managed. This occurs when the airspace is busy or if there have been delays. Aircraft enter the stack at its highest point and then spiral down until the controller is ready to feed them into the final approach to land.

    At airports like Heathrow there may be a number of stacks and the controller will draw aircraft from them to make the most efficient use of the runway.