In this photo from NASA we can see the ash going from Eyjafjallajökull over the Faroe Islands and the Shetland Islands. The ash halted most planes in Europe and the WHO warned about the dangers of the ash.
The volcano has a history of blowing ash out for long periods at a time. Fears of Katla erupting have risen because Katla usually erupts after Eyjafjallajökull.
NASA image by Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC (Public Domain)