Meanwhile Scandinavian-based airline SAS said it would have to consider temporary lay-offs of staff if the travel shutdown continues into a second week.
Hardest-hit are European airlines, but the airspace shutdown has also forced the cancellation of flights from Asia, the Middle East, the US and Canada, and as far away as Australia and South America.
Aviation experts say the tiny particles of volcanic debris carried high in the atmosphere pose a potentially catastrophic threat to aircraft engines.
Meanwhile volcanologists have warned that the eruption could last for many more days or even months, threatening drawn out travel chaos and a deepening financial cost.
A previous eruption by the same volcano lasted a year.
On Friday officials at the Association of European Airlines (AEA) criticised the varied response by national governments to the ash plume.
"No one questions that volcanic ash poses a threat to safety," said the association's secretary general Ulrich Schulte-Strathaus.
|With flights grounded rail firms have seen a surge in sales [AFP]
"But we are concerned that different criteria may be applied by different authorities to determine if and when their airspace will be closed, and equally importantly, re-opened for aircraft," he said.
"The damage that results to the Western European economy is huge, since the infrastructure that European airlines provide is vital."
The group said it believed Europe's economy had already lost around a billion euros due to the airspace shutdown.
"The Belgians simply shut up shop, and did so apparently long before their airspace was contaminated," David Henderson, a spokesman for the AEA, told the AFP news agency.
"The Germans seem to be approaching it a bit more pragmatically," while the British appeared "ultra-cautious," Henderson said.
"Nowhere does anyone seem to have taken into account the density of the particles in the cloud, and at what point their concentration ceases to be critical."
But while the airline industry is bracing for a heavy financial hit from the shutdown, other businesses are reporting a sudden boom in trade.
Ferry and rail firms have seen a surge in ticket sales and in the UK one leading taxi firm has reported a spike in inquiries from customers wanting to book chauffeured cars for urgent travel across Europe.