A volcanic eruption in the southwestern part of Iceland's Eyjafjallajoekull glacier has released a significant volume of ash into the air.
Experts say the tiny particles of rock, glass and sand contained in the ash cloud from the still-erupting volcano could jam aircraft engines.
Flights across much of Europe are being cancelled on a second day of massive disruption.
The second eruption began on Wednesday, but activity was seen already on 9 April, as Danish teacher Kurt Christensen's picture, taken near the volcano, shows.
The volcanic ash plume is spreading from Iceland to the north of Britain.
This enhanced colour satellite image, seen at the Met Office headquarters in Exeter, England, highlights the path of the drifting ash.
Emergency officials said the eruption under the ice cap was 10 to 20 times more powerful than one last month.
While geologists predict there is a much greater risk of widespread flooding.
Met Office forecaster Philip Avery said the ash could take several days to clear.
At sunset on 14 April Marco Fulle photographed the eruptions from a helicopter as he passed over the glacier.
This radar image taken on 15 April by the Icelandic coastguard shows ash spreading from the crater of the Eyjafjallajokull volcano.
A satellite image from 24 March 2010 of the Eyjafjallajoekull volcano shows lava fountains, lava flows, a volcanic plume, and steam from vaporised snow.
What are these?