06/20/2010 05:12 am ET Updated Dec 06, 2017

New Ash Cloud Threatens To Disrupt Air Travel Recovery

Airplanes slowly returned to the skies in Europe Tuesday, but the relief could prove to be temporary as a new ash cloud is said to be spreading from Iceland, threatening to keep significant parts of Europe's airspace closed.

While some European airports reopened Tuesday, London's airports remained closed due to the potential danger of the "invisible ash cloud," the AP reports.

Europe's air traffic agency, Eurocontrol, said up to 60 percent of flights over Europe would go ahead, according to the AP.

Still, an international pilots group warned that ash remains a danger and meteorologists say Iceland's still-erupting volcano isn't ready to rest yet, promising more choked airspace and flight delays to come.

Ash that had drifted over the North Sea from the volcano in southern Iceland was being pushed back over Britain on Tuesday by shifty north winds, Icelandic scientists said.

CNN reports that the eruption of the Icelandic volcano is now strengthening, "spewing a new cloud of ash that officials said was heading toward the United Kingdom."

Here's an AP video of the volcano, which continues to spew smoke and lava.