Between 20-25 percent of flights in and out of the two main airports in Paris were cancelled Tuesday due to weather alerts and expected heavy snowfalls in the region, airport manager Aeroport de Paris (ADP) announced. Northern France has been hit by unusually-heavy snowfalls of up to 20-30 centimetres in some parts and the snowfalls are drifting further south, causing traffic problems on roads and in the air. The Paris region is being hit by snow, sleet and torrential rain, forcing the civil aviation authorities to call for the voluntary flight cancellations by airlines. The main airport at Roissy-Charles de Gaulle is expected to cancel 25 percent of all flights Tuesday, while the smaller and more domestic Orly airport is to cancel 20 percent of traffic. ADP said, however, that road access to the capital\'s airports was relatively unaffected early Tuesday by the weather conditions. The current weather pattern is expected to last through Wednesday and public services have been mobilized to tackle the heavy snow in Normandy and parts of Brittany.