Reuters: Experts disagree over how to measure the dispersal of volcanic ash and who should decide when it is safe to fly, as millions of travelers remain grounded and revenue losses top $1 billion due to the Icelandic ash crisis. “I would call it a European mess because we did not focus on figures and facts,” Giovanni Bisignani, director general of the International Air Transport Association (IATA) said on Monday. “Europe was using a theoretical mathematical approach and this is not …