DRAMATIC sunsets, aflame with red and gold, across northern Europe will have offered little compensation to airline passengers suffering the consequences of the extensive cloud of ash belching from an Icelandic volcano. Terminals empty of passengers and grounded aircraft attested to the power of nature to disrupt the travel plans of millions as many of Europe's busiest airports were forced to close for business on Thursday April 15th.

The travel chaos is set to continue for several days, even if the volcano stops erupting or the wind changes direction and blows the cloud away from Europe's crowded air space. The risk to planes comes from tiny particles of silicate that reduce visibility for pilots and, worse, could knock out a jet engine. In recent years several instances have been reported of engines cutting out after flying through volcanic clouds, though thankfully pilots have then been able to restart them at lower altitudes away from the hazardous ash.

Britain's authorities said that most of the country's airspace would be closed for a second day and at least until at least 1am on Saturday. By Friday Charles De Gaulle in Paris, and many smaller French airports; most of Germany's big airports, including Frankfurt, the base for Germany's Lufthansa; Schiphol in Amsterdam; and many smaller hubs in Belgium, Ireland and Scandinavia had closed for business. As the cloud drifted east towards Russia the Polish authorities started to close airspace there too. Eurocontrol, which oversees air traffic in Europe, expects around 11,000 flights to take off in the region today where usually there would be some 28,000. Around a third of the morning flights on transatlantic routes into Europe, one the world's busiest, arrived at their destinations.

Even if the Icelandic volcano's eruption stopped tomorrow, thousands of flights in and out of Europe and millions of passengers will be disrupted. And it may take many days to get schedules back to normal, as grounded planes and crew are redirected to the right parts of the world. The Centre for Asia Pacific Aviation, an Australian airline consultancy, reckons that around 6m passengers will be affected if, as seems possible, the disruption goes on for a third day.

The fear not just for Europe's airlines but for the continent as a whole is that the effects could last for days or even weeks. Europe's airlines have struggled through a nasty recession that led to deep losses but until Eyjafjallajökull intervened things seemed to be improving. In February passenger numbers for European airlines were 4.3% up over the year before according to IATA, the airline's industry body. And in March IATA halved its forecast for airlines losses for the year to $2.8 billion. Yet recovery in the vital transatlantic business market and shrinking short-haul travel continues to put a strain on airline finances. Losing over $200m a day to volcanic disruption will not help.

For all the signs of recovery the situation has worrying echo of the damage wrought to America's struggling airlines in the wake of the September 11th terrorist attacks in 2001. The suspension of all flights in American airspace for several days in the wake of the terror attacks forced a $15 billion government bail-out for domestic carriers. Even with this help US Airways and United Airlines were forced to file for bankruptcy in 2002. A prolonged disruption of flights in and out of northern Europe could threaten the tentative economic recovery in the region if business travellers and tourists stop arriving.

Another more immediate worry for northern Europe is the health risk that volcanic ash might bring. While the ash cloud floats miles above the earth it poses only a risk to jet engines. But reports suggest that it may have started to settle on the ground in Scotland. More could follow further south. The World Health Organisation recommends staying inside if ash starts raining down from the sky. The agency admits that the exact health worries are unclear but reckons that inhaled particles might cause respiratory problems. Moreover volcanoes spewing ash into the atmosphere can have effects on the climate too. A far larger eruption in Iceland in 1783 threw sulphur dioxide and other gases and dust into the air creating a persistent haze that blocked out sunlight.

Airlines have weathered the effects of recessions, terror attacks, wars and diseases such as SARS in the past and most will eventually get over a few days lost to volcanic activity. But a prolonged eruption could have more unpleasant effects not just for air travellers but for everyone in the region.