Hundreds of flights at airports from Lisbon to Munich were cancelled yesterday and some European airspace was closed because of a volcanic ash cloud from Iceland that caused air travel chaos last month.
All flights to the city of Porto in northern Portugal and the Azores were suspended, with normal operations expected to resume by 0600 GMT today, airport officials there said.
In all more than 200 flights were grounded in Portugal, including 71 at Lisbon's airport, where Pope Benedict XVI is due to arrive tomorrow for a four-day visit to the country.
The Vatican said yesterday the Pontiff's trip was still on schedule despite the air traffic disruptions.
"At the present time, we expect no change to the programme" of the Pope's visit, Vatican spokesman Father Federico Lombardi said.
The volcanic ash cloud's unwelcome return affected air travel across much of southern Europe, especially in France and Italy, and extended into Austria and Germany.
The airspace around the southern German city of Munich was closed at 1300 GMT, cancelling flights there and at other airports including Stuttgart, authorities said.
"Due to the high level of contamination from volcanic ash, there have been no flights taking off or landing at Munich airport," said the DFS air safety agency, adding the measures would be in force "until further notice."
Neighbouring Austria has partially closed its airspace until the early hours of today, hampering traffic at airports in Vienna, Innsbruck, Linz and Salzburg, the air authority Austro Control said.
The coordinator of air traffic control across Europe said it expected about 24,500 flights to take place yesterday, around 500 less than the average for this time of year.
Eurocontrol added that "trans-atlantic flights continue to be affected by the ash cloud", with many suffering delays as they skirt the edges of the volcanic plume.
Authorities reopened Italy's skies in the north to air traffic at 1400 GMT after shutting down its airspace earlier for about six hours as the ash cloud hovered over the peninsula, cancelling nearly 300 flights at Milan airports.
On Croatia's Adriatic coast the ash cloud forced officials to close airports at Split and Zadar at 1200 GMT.
In France, the airspace remained open Sunday but at least 70 flights bound for southern Europe were grounded at airports in Paris, Lyon, and Nice, the nearest international airport to Cannes which is to host its flagship international film festival in three days' time.
The French weather service warned that the volcanic ash cloud could drift over southern France and that it could continue to affect Europe's skies for several months.
Iceland's Eyjafjoell volcano erupted on April 14 and caused travel chaos worldwide with airspace closed over many European nations for a week in mid-April for fears the ash would damage aircraft engines with fatal results.
It was the biggest aerial shutdown in Europe since World War II, with more than 100,000 flights cancelled affecting some eight million passengers. The airline industry said it lost about €2.5 billion.
The volcano began fresh and intensive ash eruptions overnight Thursday and closed Ireland's airspace for a time, and was again affecting the island nation yesterday.
Irish airports at Donegal, Sligo and Ireland West (Knock) on the western coast were facing restrictions yesterday.