The 2010 eruption of Iceland's Eyjafjallajökull volcano had a huge impact on air travel, changing the assessment of risk by the aviation sector and catalyzing new lines of scientific investigation. Ash advisories derived from dispersion-model output were issued by the London VAAC, depicting the presence of ash over large parts of Europe and the North Atlantic. Based on those advisories, over 300 airports in about two dozen countries, and a correspondingly large airspace, were closed in Europe during 15-21 April 2010. This resulted in massive impacts on air travel worldwide. Over 100,000 flights were cancelled over that week, affecting 7 million passengers, and resulting in $1.7 billion USD in lost revenue to airlines according to an analysis by Oxford Economics.
To reopen airspace, European aviation authorities endorsed the creation of a new type of concentration chart advisory product that delineated hazard zones based on dispersion model output of ash concentrations. So called 'low' ash concentrations were deemed to be defined as <2-4 mg/m3. The concentration charts were adopted by air traffic management and airlines with the expectation that zones of low density ash could be transited with no or minimal risk of immediate aircraft damage providing a regime of enhanced risk assessment by airlines, including more frequent aircraft inspections, was adopted. Currently, concentration charts have only been adopted for operational use in Europe and the North Atlantic region, as outlined in Volcanic Ash Contingency Plan EUR and NAT Regions. The scientific validity and operational utility of the ash concentration charts have been questioned by international experts and therefore have not been implemented outside Europe.
Also in response to Eyjafjallajökull's impact on air travel, ICAO formed the International Volcanic Ash Task Force (IVATF) in May 2010, charging it to examine how best to define hazardous airspace and manage aviation risk. The IVATF included representatives from government and industry groups involved in aviation regulation, operations, and scientific investigations. The IVATF finished its work in June 2012, and a record of its results is available.
On the scientific front, there has been a notable increase in volcanic-cloud research since Eyjafjallajökull and the Cordon Caulle long-lived ash plume of 2011. A burst of scientific articles has been published, including in special journal issues (Hasager et al, 2010; Langmann et al., 2012). Overall, these eruptions have prompted the aviation industry, regulators, and scientists to work more closely together to improve the manner in which hazardous airspace is defined, forecast, and communicated.