Iceland volcano 2010

REYKJAVIK, Iceland, April 21 (UPI) -- An estimated 75 percent of the usual number of passenger flights over Europe were expected back in the air Wednesday as skies clear from volcanic ash.

Officials reopened airports across the continent a week after the eruption of a volcano under Iceland's Eyjafjallajokull glacier sent a huge plume of smoke, ash and grit into the air.

The fear that a buildup of volcanic debris could cause jet engines to fail led authorities to ground thousands of flights into and out of European airports. Millions of passengers were affected and the airline industry losses could approach $2 billion.

Airlines worked to fit the passengers who had been stranded for days onto flights. It was expected to be several days before the backlog was met and air traffic returned to normal levels.

The bulk of the flights canceled Wednesday were shorter trips.

It wasn't only travelers who were inconvenienced. Industry was also affected, the BBC said. Grounded flowers and food from Africa will likely have to be thrown out as spoiled, parts from Germany for automakers in Japan were delayed, idling plants, and goods waiting to be shipped from China, the world's largest exporter, remained in Asia.

Scientists said Wednesday the volcano at Eyjafjallajokull wasn't as active as it had been over the last week but warned such eruptions are unpredictable and could cause other nearby volcanoes to also erupt, which could spew another ash cloud dangerous to air travel.