The Spanish airport authority AENA said 15 northern airports would close from 1000 GMT until at least 1600 GMT due to high concentrations of ash.
The European air traffic agency Eurocontrol said airports were also closed or expected to close in northern Portugal and parts of southern France.
"Ash eruptions are ongoing and the area of potential ash contamination is expanding in particular between the ground and 20,000 feet," Eurocontrol said.
However, the French aviation authority said airports in southern France would remain open. "Logically, we will be spared until Monday noon, based on current forecasts," a spokesman said.
He said the French authority would give an update at 1600 GMT on Saturday.
Transatlantic flights were being re-routed around the affected area, causing substantial delays.
Sweeping closures of European airspace last month disrupted the travel plans of millions of passengers in Europe and elsewhere and cost airlines over a billion euros in revenues.
Assessments by scientists and aircraft manufacturers led to a decision to restrict closures to areas of higher ash concentration, after it was found that lower concentrations were not damaging aircraft engines
.
