The news came after European air-safety authorities agreed earlier Monday to relax flight bans that it enacted after Iceland’s Eyjafjallajökull volcano (ay-yah-FYAH’-tlah-yer-kuh-duhl) started erupting violently Thursday, spewing a cloud of fine but potentially dangerous dust high into the atmosphere. Days of airspace closures across most of northern and central Europe, the world’s biggest restriction of flights since 2001, have left more than eight million passengers dislocated and cost airlines at least $1 billion dollars.
Following criticism by airlines that authorities were being overly cautious in grounding flights, European Union officials agreed Monday to divide EU airspace into three zones based on ash concentrations in the atmosphere. European aviation authorities will establish a “limited” no-fly zone surrounded by a buffer area. Airlines will be allowed to fly outside the zone once they are opened by national authorities.Volcanic ash can badly scratch a jetliner, clog external sensors and damage jetliner fan blades. In higher concentrations, it can block the tiny holes in turbine blades and jet combustion chambers through which air and fuel pass, potentially snuffing out an engine.
But much about the impact of volcanic ash on jet engines remains unstudied. Moreover, the current eruption is different from many previous incidents because the Icelandic volcano is beneath a glacier. The interaction of heat and ice atomized the magma into much finer particles than is typical, and created a steam cloud that sent the ash higher than usual into the air.
On Monday, the volcano shifted from emitting ash to lava, Icelandic officials said, lowering the ash cloud’s altitude and potentially its threat to aviation. But the British advisory indicated that authorities remained very cautious about relaxing their ban.
Eurocontrol, an umbrella agency that coordinates air traffic across 38 European countries, said authorities will use satellite images to decide whether to open airspace, and rely less on computer models that indicated the ash cloud had spread over much of Europe. They will offer carriers scientific data on weather and volcanic ash as well as safety assessments from flights conducted with oversight from European aviation authorities.
“A low concentration of ashes is not necessarily a safety risk,” said Bo Redeborn, director of network design at Eurocontrol.
Concerns about flight safety were increased by reports that engines of a Finnish F-18 Hornet and an F-16 fighter jet operated by an unidentified country in the North Atlantic Treaty Organization had been damaged by flying close to the ash cloud. The Finnish aircraft had been flying Friday in Lapland but details of the F-16 incident couldn’t immediately be learned. A spokesman for the U.S. Air Force said no U.S. aircraft had been damaged by the volcanic ash.
Capt. Georg Fongern, an executive vice president of the International Federation of Air Line Pilots’ Associations, said Monday that additional data collection and analysis by regulators and engine manufacturers are essential before making a decision to fly in affected areas affected by ash from the eruption. Until those data are assembled, it would be “better to stay on the ground,” he said.
Some safety experts also remained skeptical about loosening the flight ban. “What they’re mainly relying on is hope that nothing bad will happen,” said David Pieri, a scientist at NASA’s Jet Propulsion Laboratory and an expert on volcanic ash and its impact on aircraft.
According to Mr. Pieri, relying on satellite images can be hazardous because they sometimes don’t indicate the precise location of ash plumes. An unusual amount of moisture in part of the atmosphere, he said, can cause satellites to miss ash particles. And even a light layer of ash that is invisible to satellite sensors or the naked eye can cause severe engine problems, he said. “I’m in the group urging caution” because the industry and regulators “don’t know enough about the long-term damage to engines.”