Revision History for USGS Fact Sheet 2010-3116 Christina A. Neal and Marianne C. Guffanti Airborne Volcanic Ash--A Global Threat to Aviation ----------------------------------------------------- Made minor improvements to pages 3, 4, and 5 January 11, 2011 Posted online at http://pubs.usgs.gov/fs/2010/3116/ December 27, 2010 -----------------------------------------------------