Europe's skies were opened for business on Wednesday, but with so many planes having been grounded by the pall of volcanic ash spreading from Iceland it could take days, or weeks, to clear the backlog.
Airlines, their flights to Europe and elsewhere idle for more than five days, counted the cost of the disruption.
Britain, a major air hub and a busy destination in its own right located squarely under the ash plume, reopened its airspace on Tuesday night, giving a boost to travelers and freight.
British Airways said on its website it would operate all its long-haul flights departing from Heathrow and Gatwick airports on Wednesday, but there would be short-haul cancellations to and from London airports until 1 p.m.
Britain's Civil Aviation Authority made clear that scientists and manufacturers had downgraded the risk of flying in areas of relatively low ash concentrations.
“The major barrier to resuming flight has been understanding tolerance levels of aircraft to ash. Manufacturers have now agreed increased tolerance levels in low ash density areas,” CAA head Deidre Hutton said.
More airlines announced the resumption of flights to Europe.
Australia's Qantas Airways said it would again be flying to Europe on Wednesday. It said the disruption had cost it A$1.5 million a day (Ł911,000).
Flights from Beijing and other Chinese cities were returning to normal. Air China, the country's main carrier, said on its website that its flights to Europe were “fully restored” from Wednesday subject to changes in weather conditions.
The business of global finance was about to return to normal, with the International Monetary Fund and World Bank announcing that a weekend meeting in Washington was going ahead.
Several world leaders cancelled or rearranged trips to Poland last weekend in connection with the funeral of Polish President Lech Kaczynski.
Air France planned to run all long-haul flights on Wednesday, Poland was reopening its airspace from 0500 GMT and Finland said it would do so from 0900 GMT. The Dutch allowed night flights after taking the lead in allowing passenger flights on Monday.
In Germany, the website for the Frankfurt airport hub on Wednesday showed a handful of early-morning flights arriving and departing but large numbers were listed as cancelled.
On Tuesday, Germany kept its airspace largely closed, although some 800 flights operated during the day, all on visual take-off and landing rules.
Britain had lagged its European neighbors in downgrading the threat to airplanes from the ash, which can potentially scour and even paralyze jet engines.
In 1982, a British Airways jet lost power in all four engines after flying through an ash cloud above the Indian Ocean.
Recriminations about what took governments so long to give the green light to an airline industry losing $250 million a day from the shutdown are likely to follow -- especially since carriers had flown successful test flights for several days.
The Association of European Airlines, representing 36 major commercial and freight carriers, criticized Britain on Tuesday for not reopening its skies sooner.
“Other people look to the UK and say 'Why are they still cautious when we are thinking of opening up?,' and of course this can influence judgments,” David Henderson, AEA manager of information, told Reuters before Britain lifted its no-fly zone.
Icelandic officials said late on Tuesday there was less activity from the volcano under the Eyjafjallajokull glacier, which has been erupting for almost a week, but strong winds could still leave Europe at the mercy of the cloud.
Raymond Benjamin, secretary-general of the International Civil Aviation Organisation, said that authorities were able to declare that the danger had passed.
An expert from the World Meteorological Organisation said in Geneva that a low pressure weather system moving into Iceland should help clear the ash cloud within days.
Freeing up the flights was a welcome respite for the airline industry, which said its losses were worse than after the September 11 attacks on the United States. But with aircraft and crew scattered where they were grounded, timetables will be wrecked.
“To get back to normal levels of operation from an (airline) industry point of view will take weeks,” British Airways chief executive Willie Walsh told BBC television.
Some poignant moments emerged from the turmoil.
A Slovak couple stranded in Taiwan got married on Tuesday at a hotel near the island's major airport after they failed to get home for a long scheduled wedding, hotel staff said.
When the man, 32, and woman, 31, were found weeping in the Orchard Park Hotel, the manager offered to set up a wedding on site, inviting clergy from a nearby university and packing the venue with 100 people, including other stranded Europeans.
But for some who have faced epic journeys and huge financial outlay, the decision came too late.
For Meg Newman, 31, a speech and language therapist, and Harry Speller, 30, both of London, said the shutdowns had forced a 16-day stay in New York and taken them well over budget. New York had been the last leg of a three-month tour through India, Nepal and Malaysia after Speller lost his accounting job.
New York itself is losing about $3 million a day in reduced spending, according to city officials.
The European aviation control agency Eurocontrol said about half of scheduled traffic in Europe had been expected to operate on Tuesday: about 14,000 flights, up from a third on Monday.
The economic impact of the cloud could potentially dent the fragile recovery from the global recession.
PricewaterhouseCoopers estimated a week of disruption could destroy around 0.025% - 0.05% of annual British GDP, and the same would probably be true of other European countries.
Luxury carmaker BMW said it was stopping production at some German plants due to a lack of electronic component deliveries. Nissan Motor Co is halting production on three lines in Japan.
Humanitarian flights were also affected.
The US military is evacuating war-wounded from Afghanistan to a base in Iraq, instead of sending them to Germany. A polio immunization campaign in West Africa was delayed because the vaccines are stuck at French and German airports. (Reuters)