BERLIN – Airlines lost at least $1.7 billion in revenue during the volcanic ash crisis, an industry group said Wednesday, as the debate heated up over whether European governments were justified in shutting down their airspace for so long.

Planes were flying into all of Europe’s major airports — London’s Heathrow, Paris’ Charles de Gaulle and Germany’s hub at Frankfurt. Still, experts predicted it could take days — even more than a week — to clear a backlog of stranded passengers after about 102,000 flights were canceled around the world.

Eurocontrol, the air traffic control agency in Brussels, said 21,000 of the continent’s 28,000 scheduled flights were going ahead Wednesday. Air traffic controllers lifted all restrictions over German airspace, but some restrictions remained over parts of Britain, Ireland and France.

Spain, which has remained mostly open throughout the crisis, developed into a key emergency travel hub, arranging for hundreds of special flights to move more than 40,000 people stranded by the travel disruptions.

Britain’s transport secretary, Andrew Adonis, denied that the government decided to reopen the skies to air travel under pressure from airlines.

“They have obviously wanted to be able to fly their planes — of course they have — but that has not been the issue at stake here,” he told the BBC.

But British Airways initiated a showdown Tuesday by announcing it had more than 20 long-haul planes in the air and wanted to land them in London. Despite being told that British airspace was firmly shut, radar tracking sites showed several BA planes circling in holding patterns over England late Tuesday before the surprise announcement that airspace was being reopened.

“We were circling for about two hours,” said Carol Betton-Dunn, 37, a civil servant who was on the first flight to land at London’s Heathrow from Vancouver.

She said passengers were initially told the flight would be going to London, then that it was heading for an unspecified European airport, then that it was going to Shannon airport in western Ireland.

“It’s been exhausting,” Betton-Dunn said.

The British Airways chief was unrepentant.

“I don’t believe it was necessary to impose a blanket ban on all U.K. airspace last Thursday,” said BA chief executive Willie Walsh. “My personal belief is that we could have safely continued operating for a period of time.”