Why some flights are delayed in bad weather, and others – no?
"There will be a flight delayed or not – depends on many factors. For example, the following three conditions are taken into account: aircraft equipment and destination airport in accordance with ICAO standards (International Civil Aviation Organization); preparation of the crew for flights in complex meteo conditions; Weather at airports departure and landing, on spare airfields.
According to ICAO standards for each port, three categories of landing minima are prescribed, that is, permissible values for visibility range. Pulkovo, for example, as an international status airport – "all-weather". The runways are equipped with radio beacons and lighting equipment, which are required for planting aircraft in conditions of minimal visibility.

To take these signals, aircraft must have the desired equipment, and to safely plant a strip, pilots – to be professionals.
To the main factors necessary for flight safety (especially with poor weather), you should add another: the state of the runway. First of all it is determined by the clutch coefficient. Even if the required equipment is installed on the lane, but it is snowing, the strip and cargo tracks should be quickly cleared. In Pulkovo, two independent stripes and modern park of airfield equipment. In winter, during the snowfall, the strips are cleaned in patrol mode, without stopping. While a snow removal caravan of 10-12 machines clears one (it takes up to 35 minutes with high snow), the second takes and sends aircraft. Then the technique moves to the second strip, and then back. This allows the airport to work as usual, without delay flights. Over the past five years, Pulkovo never closed due to meteo conditions ".