Published: Apr 15, 2010 4:54 PM EDT

      Air traffic across much of Europe is grounded today by an ash cloud from a volcano in Iceland.
      Thousands of flights have been canceled, with tens of thousands of people stranded.
      Officials say it's not clear when it will be safe enough to fly again. One scientist says the volcano could continue to send up ash for days or even weeks.
      A statement from civil aviation authorities in Londony said the "cloud of volcanic ash is now spread across the U.K. and
continuing to travel south."
      The statement said the Icelandic volcano was sending up smoke and ash that posed "a significant safety threat to aircraft," as visibility is compromised and debris can get sucked into airplane engines.