Fog is one of the most problematic weather conditions for air traffic controllers. Very thick fog reduces visibility at airports, therefore requiring pilots to be extra vigilant in order to land or take-off safely.
As François Chevrier, an air traffic controller explains, in fog, except for accredited vehicles, no vehicle circulates on the ground, and all work stops. The runway is strictly reserved for aircraft.
To be able to land in fog, therefore in poor visibility conditions, aircraft and airports must, in particular, be equipped with special equipment, called an instrument landing system (ILS: instrument landing system or GNSS: Global Navigation Satellite System). Pilots must also have the necessary qualifications, otherwise, aircraft are obliged to divert to another airport.
Normally at this airport two runways operate, today only one is open to facilitate the work of the air traffic controllers. This is a security measure that slows down air traffic. One other measure to avoid accidents at the airport when visibility is below 1,800 feet (550 metres), the interval between landings and take-offs is multiplied by two, i.e., 6 minutes instead of the usual 3.
With the arrival of winter, frequency of fog phenomena can be expected, leading to the probability of flight delays in the coming four months.