This article is by Alan Cowell, Liz Robbins and Nicola Clark.

PARIS — The menacing cloud of ash from a volcano in Iceland moved eastward across Northern Europe on Friday, expanding an already massive transportation gridlock and throwing weary travelers into an anxious limbo.

Scientists were uncertain when the cloud would dissipate, as its repercussions rippled far beyond the flight boards at shuttered airports in Europe.

Opera singers and musicians were stranded while trying to make their performances, and perishable foods were stuck in warehouses. Thousands of people unable to travel by air jammed train stations or hired long-haul taxis in a desperate search for alternative ways to reach their destinations. Recreational runners in Europe grew worried they would not be able to reach Boston early Monday in time for the start of the Boston Marathon.

From business meetings to long-planned high school trips to world diplomacy, the ash cloud affected many facets of life. The state funeral of the Polish president, Lech Kaczynski, and his wife was likely to take place as scheduled on Sunday, according to Polish authorities, but it was unclear which international dignitaries would be able to get there.