Volcano Monitoring

Civil aviation authorities closed airspace and shut down airports in Britain, France, Scandinavia and other parts of Europe on Thursday as a high-altitude cloud of ash drifted south and east from an erupting volcano in Iceland.

The shutdown, among the most sweeping ever ordered in peacetime, forced the cancellation of thousands of flights and left airplanes stranded on the tarmac at some of the world’s busiest airports as the rolling cloud — made up of minute particles of silicate that can severely damage airplane engines — spread over Britain and toward continental Europe.

The volcano erupted Wednesday for the second time in a month, forcing evacuations and causing flooding about 75 miles east of Reykjavik. Matthew Watson, a specialist in the study of volcanic ash clouds from Bristol University in England, said the plume was “likely to end up over Belgium, Germany, the Lowlands — a good portion over Europe” — and was unlikely to disperse for 24 hours.

British aviation officials said the country’s airspace would remain closed at least until 7 a.m. local time Friday, meaning that only authorized emergency flights would be permitted. All of the roughly 6,000 scheduled flights that use British airspace each day would be affected, aviation experts said.

Deborah Seymour, a spokeswoman for Britain’s National Air Traffic Service, said the closure of the country’s airspace was the most extensive in recent memory. “It’s an extremely rare occurrence,” she said, noting that British airspace remained open even after the September 2001 terrorist attacks in the United States, with the exception of a no-fly zone over central London. She said there had been some brief airspace closings because of technical system failures in the past, but “nothing of this magnitude.”

Seven British Airways flights that departed Wednesday evening to Britain had to turn back after flying less than halfway, according to John Lampl, a British Airways spokesman in New York. They had departed from Chicago, San Francisco, Denver, Mexico City, Calgary, Vancouver and Las Vegas, Mr. Lampl said.