Germany's Lufthansa have carried out test flights through the ash cloud. They reported no damage to their aircraft, however air space in around 20 countries remains closed, affecting millions of people's travel plans. Forecasters believe disruption's likely to continue for several more days as light prevailing winds are failing to clear the cloud. The volcano in the south of Iceland began erupting on Wednesday, sending plumes of ash several kilometres into the air. Scientists have warned it could trigger a chain-reaction in other volcanoes in the country.