European air traffic centres are bracing for possible operational disruption after an eruption by the Icelandic volcano Grimsvotn.
The volcano is the same one used as a basis by Eurocontrol to mount a test exercise in April of new ash crisis procedures, introduced to avoid a repeat of last year's blanket airspace closures when the Eyjafjallajokull peak in Iceland erupted.
Eurocontrol's Central Flow Management Unit stated that it had been advised of the eruption by the Icelandic meteorological office. "The plume height has been confirmed by aircraft [to be] 12km or higher," it added.
Iceland's meteorological office said the eruption started at 17:30UTC and put the plume at up to 20km. "Initially, the plume is expected to drift to the east and subsequently to the north," it said. "The ash is not expected to impact aviation in Europe, at least not during the first 24 hours."
Grimsvotn is located about 220km east of Reykjavik, the capital of Iceland. The meteorological office said the volcano last erupted in November 2004.
Ash concentration forecasts by the London-based Volcanic Ash Advisory Centre suggest a broad dispersal of ash over and around Iceland by midnight on 23 May, with concentrations above 4,000 microgrammes per cubic metre, at flight levels below 20,000ft.
But for higher cruising altitudes this level of ash concentration appears to be primarily towards the north of the country.
"[There is] no threat to air travel yet," said Eurocontrol.
Initial results from the exercise conducted on 13-14 April, to test the revised volcanic response procedures, indicate that 70% of all planned flights would have taken place - a trebling of the number permitted to become airborne during last year's ash crisis.