Geneva ? Airlines canceled hundreds of flights across Europe and added hours to trans-Atlantic journeys Sunday as planes were diverted around a large plume of ash spewed by an Icelandic volcano and stretching from Greenland to Portugal.

So far, the weekend cancellations have been a fraction of the flights nixed two weeks ago when jittery European air traffic authorities closed down much of the continent’s airspace for fear the volcano’s abrasive ash could harm jet engines. But the possibility loomed of continuing eruption, and rising costs to airlines from ongoing disruption.