LARGE parts of northern Europe have been turned into a no-fly zone after ash from a volcanic eruption in Iceland grounded thousands of flights.Britain closed its airspace to all flights yesterday and nearly every airport in Norway, Denmark and northern Sweden also shut, authorities announced.Big disruptions also occurred in Belgium, France, Finland, Germany and the Netherlands.The safety authority Eurocontrol said up to 4000 flights would be cancelled yesterday.Britain’s National Air Traffic Service said it was “unlikely the situation over England would improve” quickly.Many flights from the rest of Europe to North America would have to be rerouted because they normally go through British airspace, officials said.Two Qantas flights from London had left an hour early, and five flights were headed to their scheduled Asian stopovers last night. “We’re assessing the situation as it progresses,” a spokeswoman said.The ash was about 10kilometres in the air and could not been seen from the ground. But experts said it posed a dangerto jet engines and restricted visibility.Forecasters have warned that the ash could take days to disperse. “The concern is that as well as the eruption, the jet stream passing through Iceland is passing in a south-easterly direction, which will bring ash to the north of Scotland and Denmark and Norway,” a forecaster for MeteoGroup said.Icelandic airports remained open as wind took ash away from the island.”Flights to and from Iceland are still OK. The wind is blowing the ash to the east,” the Icelandic Airport Authority said.The eruption of the Eyjafjallajokull volcano in south-east Iceland on Wednesday had already melted part of a surrounded glacier causing severe floods. More than 700 people were evacuated from their homes.Ellie Harvey and agencies