Spain is to close 15 airports as a cloud of ash from an Icelandic volcano drifts south over Western Europe.
National airport management agency Aena said nine airports were already closed and six more would shut from 1200 local time (1000 GMT).
The restrictions would be in place until at least 1800, Aena said
Most flights between Europe and North America are being diverted because of the ash cloud's latest drifting, officials at Eurocontrol said.
Flights are being rerouted north and south of the 1,200 mile (2,000km) cloud.
On average, 600 airliners make the Atlantic crossing every day, correspondents say.
Aena said the airports affected were Bilbao, San Sebastian, Vitoria, Zaragoza, Pamplona, La Rioja, Santiago, A Coruna, Vigo, Asturias, Santander, Leon, Valladolid, Burgos and Salamanca.
Eurocontrol, the agency that co-ordinates aviation safety in Europe, said airports were also expected to close in northern Portugal and parts of southern France.
Last month, thousands of travellers were stranded after ash shut down airspace across Europe.
Recent images have shown activity in the Eyjafjallajokull volcano intensifying.
Experts at the UK's Met Office said it was sending ash up to heights of 30,000 ft (9,100m).
Flights across Ireland and parts of the UK were disrupted earlier this week.
Source: BBC News