Ash from the erupting Icelandic volcano has halted a single flight over Greenland , but the most of it was expected to blow north of Scandinavia and disrupt few, if any, flights over Europe.
Danish air traffic said the ash from the Grimsvotn volcano reached eastern Greenland forcing Air Greenland to cancel its daily flight to Copenhagen.
Aviation officials in Norway said the cloud might also affect flights to and from Svalbard.
In Britain the Met Office said the ash may reach British airspace later this week but the European air traffic control agency said it was not expected to move further than the western coast of Scotland.
In April 2010, the Eyjafjallajokull eruption prompted aviation officials to close Europe's airspace for five days out of fear that the ash could harm jet engines. Thousands of flights were grounded, airlines lost millions and millions of travellers were stranded, many sleeping on airport floors.
Eurocontrol's models of ash concentration in the latest case showed the main plume of ash at heights from 20,000 feet to 35,000 - the normal altitudes for passenger airliners - gradually extending northward from Iceland over the next two days. The cloud is predicted to arch its way north of Scandinavia and possibly touch the islands off the northern Russian coastline within the next two days.
A smaller plume could reach as far as the western coast of Scotland during that period, and the eastern coast of Greenland.
Iceland shut its main airport after Grimsvotn, about 120 miles east of Reykjavik, erupted on Saturday.
Neither plume is projected to reach the European mainland. They are also not expected to affect trans-Atlantic flights, whose eastbound and westbound tracks are located further much south of the projected ash dispersal.
Some airline chiefs complained that regulators over-reacted last year. But a study last month in the Proceedings of the National Academy of Sciences concluded the shutdown had been justified. It said the hard, sharp particles of volcanic ash blasted high into the air could have caused jet engines to fail and sandblasted plane windows.