The unprecedented closure of airspace across Britain and large parts of Northern Europe is set to continue into the weekend, after the volcanic eruption in Iceland that sent a massive plume of ash into the atmosphere.

As debris continued to spew from the Eyjafjallajökull volcano, airlines were last night preparing to ground flights for at least four more days.

Hundreds of thousands of stranded passengers, already experiencing the worst travel chaos in living memory, faced trying to make alternative arrangements by rail, road or sea — or cancelling their trips.

The National Air Traffic Service denied that it had overreacted by closing UK airspace. It said: “Safety is our main priority and volcanic ash is a serious threat to aircraft.” Safety experts said that if the ash is sucked into jet engines it can cause them to fail catastrophically. (TIMES ONLINE)

Passengers may not have been able to see see the source of their frustration — except indirectly, when the ash created vivid red and lavender sunsets. The cloud is almost invisible to the eye. It began to spread across Europe in the early hours of Wednesday before stretching east to Norway, Sweden and Finland and south across Scotland and the UK, engulfing Britain totally by Thursday afternoon.

The prevailing northwesterly wind is forecast to continue for at least four days, and the ash already in the atmosphere will take between 24 and 36 hours to drift across Britain, the Met Office said. The ash was expected to reach ground level in Britain last night, starting in Scotland, according to NHS National Services Scotland. “It is important to stress that the concentration of particles which does reach ground level is likely to be low and should not cause serious harm,” it said.

“If people are outside and notice symptoms such as itchy or irritated eyes, runny nose, sore throat or dry cough, or if they notice a dusty haze in the air or can smell sulphur, rotten eggs, or a strong acidic smell, they may wish to return indoors.”

The volcano began erupting on Wednesday for the second time in less than a month, triggering floods and shooting smoke and steam miles into the air. About 700 people from rural areas near Eyjafjallajökull were evacuated yesterday due to flash flooding, as water carrying chunks of ice the size of houses crashed down the mountain.

Video footage from the scene shows spectacular images of hot gases melting the thick ice, and sending cascades of water thundering down the steep slopes of the volcano. When the volcano on the southern tip of Iceland was last active, in 1821, the eruptions continued, on and off, for two years.

Einar Kjartansson, a geophysicist at the Icelandic Meteorological Office, said: “It is likely that the production of ash will continue at a comparable level for some days or weeks. But [how much] it disrupts travel, that depends on the weather.”

Geophysicists in Iceland were alerted to tremors below the peak of the volcano, 75 miles (120km) east of Reykjavik, just before midnight on Tuesday. They were far stronger than some last month, and the released magma melted a hole through 650ft (200m) of ice covering the crater.

By 7am on Wednesday, the airborne debris, more than 20,000ft high, had started to move slowly southeast. Forecasters initially hoped the cloud would be carried past most of Britain, but by the early hours of yesterday they began preparing for the worst.