As the main hub carrier at Zurich Airport, SWISS operates both short- and long-haul flights to offer attractive connections for its transfer passengers. When the airport’s capacity is constrained, the Network Manager Operations Centre (NMOC), in collaboration with skyguide, the Swiss air navigation service provider, normally assigns air traffic flow management (ATFM) restrictions for inbound flights, following specific attribution rules.
The problem here is that the NMOC has no information about either the airline’s commercial schedule or the number of transfer passengers who will be affected by a restriction on a particular flight. Only SWISS has an idea of the number of possible passenger misconnections that an ATFM restriction might entail.
The result is all too often very short connecting times for passengers. This could be avoided if the impact on transfer passengers had been taken into account in the regulation assignment process.
Besides, a delay will also affect an aircraft’s connecting time to its next planned sector. Since an aircraft is normally scheduled to operate several flights in a row, its daily schedule will be particularly challenged by any ATFM restrictions that are imposed early in the day, during the so-called ‘first rotation hours’.
In contrast, ATFM restrictions imposed late in the afternoon cause less reactionary disturbance, as the same aircraft will have fewer flights left to carry out before the night movement ban. In either case, however, given that any deviation from the plan normally leads to a higher degree of complexity for transferring passengers, it is vital that planned aircraft schedules are followed as closely as possible.