Airspace closures should be an action of last resort in the event of volcanic ash contamination, according to new advice issued by the European Aviation Safety Agency (EASA).

With one eye on another potential eruption from an Icelandic volcano, the agency has told operators that airspace closures should be “contemplated only in situations in which the Volcanic Ash Safety Risk Assessment approach can no longer be relied upon to secure safe operations.”

It said that member states in the immediate vicinity of a volcano may decide to close airspace where “volcanic ashes and gasses form a direct threat for the safety of flight.”

The move comes as Icelandic authorities maintain a second highest alert—orange—for a potential impact on aviation from the Barðarbunga (Bardarbunga) volcano in southeastern Iceland—one of the country’s largest volcanic systems.

Thousands of earthquakes have been recorded in the vicinity of the volcano since Aug. 16, indicating a possible impending eruption. Scientists recorded a particularly strong quake, measuring 4.7 on the Richter scale late on Aug. 21, the strongest yet recorded during the period of earthquake swarms.

Furthermore, the Italian volcano Stromboli, off the northern coast of Sicily has also begun erupting in recent days.

EASA said that when ash is forecast to be present within European airspace, operators can conduct flight operations in areas with medium- or high-forecast ash contamination only if they have established a safety risk assessment for such operations. However, the agency said that flight operations should be avoided in areas where volcanic ash is visible or where visibility of ash is impaired, such as at night.

If an ash cloud forms, the agency is calling on the two European Volcanic Ash Advisory Centers (VAAC) in London and Toulouse to provide forecasts depicting areas of low, medium and high ash concentrations.

The agency also suggests that—in the event of an eruption and flight operations in areas of low ash concentration—operators should carry out further inspections for accumulation of ash, erosion of components or system damage.

“Unless specific instructions have already been provided by aircraft and engine Type Certificate holders to be applied after encountering a volcanic ash … inspections should also be performed after each flight,” the agency stated.

Eurocontrol said staff is monitoring the situation and European air traffic authorities are ready to respond should the volcano erupt.

The service said operational responses developed as a result of the 2010 eruption of Eyjafjallajökull, which caused more than 100,000 flights to be disrupted over six days, mean that air navigation service providers are now better prepared than they were in 2010.