Flights have been disrupted across northern Europe by volcanic ash drifting south and east from Iceland.
Authorities were closing down UK airspace. Flights were also disrupted in Norway, Sweden, Finland and Denmark.
The ash, which can damage aeroplane engines, was produced by a volcanic eruption under a glacier in Iceland.
Flooding was reported as the glacier melted, with as many as 800 people evacuated from their homes in the south-west of the island on Wednesday.
Eyewitnesses and local officials said there were two flows of flood water coming off the glacier, and that a road along the flooded Markarfljot river had been cut in several places.
By Thursday morning, the disruption to air traffic stretched from the UK to Scandinavia.
'Large floods'
Oslo airport, which is Norway's largest, was closed, while Finland's airport agency Finavia said air traffic to northern Sweden and northern Finland was also affected.
In Denmark, officials said airspace would be closed from 1800 (1600 GMT).
The Air Traffic Control Service (Nats) said no flights would be allowed in or out of UK airspace from midday to 1800BST (1100-1700 GMT) amid fears of engine damage.
Airports in Scotland had already been shut earlier on Thursday and flights at several English airports had been suspended.
The last volcanic eruption at the Eyjafjallajoekull glacier was on 20 March - the first since 1821 - and it forced about 500 people in the sparsely populated area from their homes.
Iceland lies on the Mid-Atlantic Ridge, the highly volatile boundary between the Eurasian and North American continental plates.
A group of Norweigians including the ambassador who were camping near the volcano were among those expecting to be evacuated late on Wednesday.
"There are large floods on both sides of the volcano, and the road in (to where they are) is blocked and the whole area is isolated due to the floods," said Per Landroe, a spokesman for the Norweigian embassy.
"There are fears that a large bridge will break," he told AFP.
