Airing and ventilation are two different things. Ventilation is a continuous process through many small openings and cracks that occurs throughout the day.
By airing on other hand is meant that the doors and / or windows are put open opposite to each other, in order to refresh the whole air supply in the house thoroughly. It is recommended to this fifteen minutes a day, also in autumn.
A good moment for additional airing are during cooking, during or after a party, when using a condenser dryer or if there is laundry drying, especially if they are hanging on radiators. Airing can’t be seen as a substitute for ventilation; even if you are airing regularly open vents are necessary to keep air flowing throughout the property.