This ash cloud is a good reminder of British Airways' City of Edinburgh's flight that almost went down in an ash cloud, leading to the Captain's famous statement while the plane was gliding:

"Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them under control. I trust you are not in too much distress."

More information: http://en.wikipedia.org/wiki/British_Airways_Flight_9

While the lack of flying now may result in missed opportunities for additional British understatement, perhaps it will keep everyone safer than they would be flying aloft.