Winter - a challenge for aviation

Jari Pöntinen, Director General for Civil Aviation, Traficom, Finland
May 2020

Kari Siekkinen, Chief Advisor, Traficom, Finland
May 2020


Winter conditions in Finland and other parts of northern Europe from October to March are challenging compared to the conditions in central and southern Europe. In northern Finland, temperature often drops below -20°C and temperatures close to -30°C are not rare; occasionally temperature even drops to -40°C. There is often also great variability in temperature, which may raise from very low to close to zero degrees just overnight creating a very different scenario and challenge. There is typically also plenty of snow and ice – up to 150 cm in the north and up to some 70 cm in the southern part of the country.


As winter weather conditions are challenging for society in general, they are especially challenging for aviation, which from society's point of view is vital for local economies and accessibility of the regions. It is not only the operation of the aircraft that needs to be considered but also issues such as ATM capacity, transfer times, airport functions, maintenance, etc. To overcome challenges posed by winter we must take a holistic and collaborative approach.

Airport operations are a combination and collaborative decision-making (CDM) process of several functions and partners. Airlines, air traffic control, handling agents and airport maintenance form a complex network of functions supporting safe and efficient operations. In addition, the central flow management unit (CFMU) plays an important role in relation to flight planning and regulating traffic in accordance with the capacity limitations at airports as necessary. The importance of the CDM must be highlighted in the challenging winter operations, as the timely coordinated actions of different entities are essential for successful operations.

What are the stakeholders' solutions for safe and successful winter operations?

For airlines, having well-trained and experienced personnel with a proper attitude towards safety is paramount. In the airlines, pilots are closest to the actual operation of the aircraft; however, they are not the only ones who must be trained for winter operations - all other operational personnel need to be too. A good safety culture must be in place and all personnel must understand the challenges related to winter operations. Pilots have their basic theoretical training for winter operations in the form of operator-specific training and type-related training for aircraft type-specific issues, but it is important to understand that real-life experience really makes a professional.

There are performance-related issues to be considered, as runway contamination and condition (poor friction levels or not fully visible touchdown markings because of snow and ice, etc.) cause restrictions for take-off and landing. To minimise the risk of runway excursion, it is essential to make sure that the approach is stabilised when the runway friction is at an average level or even lower.

Company safety culture, which starts with senior management, is essential when pilots face operative conditions where they need to make a decision to divert instead of making approach and landing under possibly unsafe conditions.

Whether the reason for diversion is a crosswind component, runway contamination or condition e.g. friction levels and/or length of landing runway, etc., it is essential for safe and successful winter operations to have no organisational pressure in the operative environment. Pilots are not alone in facing the challenges of winter operations; airworthiness personnel such as mechanics, who face e.g. problems related to cold temperatures in engines, as well as flight planning personnel who need to be aware of the chain effects of delayed departures and arrivals caused by clearing the runway of snow (such as the need to re-route passengers) are also concerned.

It is important for all parties to understand how the reported weather and runway conditions actually affect flight operations. The aim of the maintenance crews is to time runway maintenance according to air traffic needs. However, flight planning must take into account the possibility that the conditions prevailing at take-off or landing time may be significantly different from the information in the SNOWTAM, because changes in conditions can be rapid. Besides runways, the taxiways and aprons may also be partly or entirely covered with snow and ice. In extreme winter conditions, diversions to alternative airports as well as delays in departures are much more likely than in the summer conditions.


As for the others, winter conditions often create challenges for air traffic control. ATC challenges are mostly related to snowfall. Heavy snowfall often reduces visibility so low visibility procedures need to take place. In this situation, the air traffic controllers' workload increases significantly because of the increased coordination with the airport maintenance crews. In order to clear snow from the runways in these weather conditions, maintenance crews need access to active runways frequently, which leads to a high number of communications via RT and calls for enhanced vigilance from air traffic control in order to properly monitor vehicle movements in safety critical areas (runways).

From the ATC point of view, a proper and timely coordination between the different ATC units (TWR, APP and ACC) is vital for success. This is important as the sequencing and spacing of the arriving and departing aircraft must be managed so that the maintenance crews can enter the runway as needed to clear the snow and spread runway de-icing chemicals if required. In the case of snowfall, the air traffic control tower is a critical coordination point for distributing and exchanging information between airport operator, airlines, ATC units and the MET provider. In the locations where extreme winter conditions occur, it is important to ensure proper basic training and refresher training for air traffic controllers, highlighting the characteristics of winter operations.

Under challenging winter conditions, proper de-icing is an essential element of flight safety. When there is reason to suspect that frost, ice or snow is adhering to aircraft surfaces, the need for de-icing must be determined. This must be done from a point offering good visibility of the aircraft surfaces. Once the need for de-icing has been determined, the pilot-in-command is responsible for deciding whether de-icing treatment is necessary. The ‘Clean Aircraft Concept' ensures safe flight operations. In all operations, the pilot-in-command is responsible for assessing whether the aircraft is safe.

Handling agents have many different roles in the safety and service chain for winter operations. A good example of a safety-related task is de-icing. De-icing personnel have a great responsibility in ensuring flight safety. They do the contamination checks of critical surfaces (like wings, stabilisers, etc.) independently supporting and complimenting the visual checks performed by the pilot. Whenever there is contamination that has to be removed and surfaces to be anti-iced, the de-icing personnel is solely responsible for determining whether the result of the de-icing is acceptable.

Airports are extremely complex environments with a great number of actors with safety-related tasks, and winter conditions add to this complexity. It is therefore important that clear procedures are documented and followed and that all personnel is appropriately trained for the winter operations and tasks they are expected to perform. The key elements for successful and safe operations are proper training, documented and tested processes, a well-functioning safety management system and good safety culture. This is a team effort!

Helsinki Airport key facts and figures related to winter operations:

  • Helsinki-Vantaa, the main airport in Finland, is well known for its excellence in managing winter operations.
  • For snow clearing and runway de-icing tasks, there are some 60 specifically designed vehicles in use.
  • To completely clear one runway and runway exits from snow takes 11 minutes with 9-10 sweeper vehicles moving side-by-side.
  • There are more than 100 people operating snow removal vehicles in the winter season.
  • There are 26 pre-designed modes of operation for snow clearing, of which the most efficient will be chosen depending on the runway combination in use and other relevant elements.
  • As a rule of thumb, the sweeper vehicles need to enter the runway once an hour in cases where snowfall is less than 1 cm (wet) snow. In cases of heavier snowfall, they need to enter the runway more often.