After the ash fell, it was relatively easy for the wind to move it due to its small grain size, and therefore large ash clouds could form even though no ashfall from the plume was happening in the area. This continued for months after the eruption, especially during storms and after long dry spells, and caused wind erosion and affected air quality in large areas. The ash was not confined to the vicinity of the volcano, as ash fell in almost every part of Iceland and large ash plumes were transported over Europe. The ash distribution away from Iceland can be split into two main stages, where ash plumes reached mainland Europe. The first stage was during phase I of the eruption, where fine ash was carried over northern, central and eastern Europe by upper tropospheric winds. Later, during phase III, ash went over the north Atlantic and western Europe. The ash plumes impacted air travel to and from 23 European countries and over 100.000 flights were cancelled during the eruption. This was the first time that ash reached mainland Europe from Iceland since the Hekla eruption in 1947. Three things came together to spread the ash over Europe; 1. The prolonged duration of the eruption; 2. the small particle size of the ash which can be suspended in the air for several days, long enough for it to be carried over Europe; and 3. The unusually frequent north-westerly winds, causing ash plumes to travel to the south and southeast away from Iceland and towards Europe.