Was Chicken Little right? European conservatives and libertarians are asking pointed questions about the extent of the air traffic shutdown. There's a good summary of that point of view, with links, in the blog of the Telegraph's Brussels correspondent, Bruno Waterfield.

What's at stake is the concept of the Precautionary Principle. A pro-Government editorial in the Independent defends the decision, with some good comments.

Watch the expert post-mortems on Eyjafjallajökull. This isn't only about volcanoes and aircraft. It's about dealing with all uncertain risk, including nuclear power, anti-terrorism measures, earthquake and tsunami predictions, and vaccines and quarantines during epidemics. In Germany, homeland of the Precautionary Principle, Der Spiegel recently blasted "the Swine Flu Panic of 2009," praising Poland's health minister, Ewa Kopacz, for resisting international calls for mass vaccination -- ironically, on grounds of "first do no harm."

Scientific and engineering organizations will be studying the response to Eyjafjallajökull for years. Whatever the outcome, their findings will help shape how governments deal with future uncertain risks. Already at least one respected NGO voice, the director of the Carnegie Endowment's European Center in Brussels, shares his second thoughts:

"Europe is the victim of the precautionary principle," Mr.[Fabrice] Pothier said, of "an uncoordinated overreaction to possible risk." That led to a huge oversupply in swine flu vaccine, for instance, and, as Mr. Quatremer noted, the European aversion to genetically modified grain.

"It's the same principle for the ash cloud," he said. "We fear everything and want maximum safety for our citizens," just like the way in the United States, he said, the society will go to extremes to protect citizens from terrorism. "No one can argue with security," he said.