By Michael Holden and Omar Valdimarsson
LONDON/REYKJAVIK (Reuters) - Northern Europe is set to again bear the brunt of air traffic disruption from Icelandic volcanic ash on Wednesday after 500 flights were canceled on Tuesday, but experts said the eruption was rapidly dying down.
The ash from the Grimsvotn volcano has caused far fewer problems than ash from an Icelandic volcano last year, when more than 10 million people were hit by a six-day European airspace shutdown. Airlines put their revenue loss at $1.7 billion.
But the new volcano has exposed disarray among the people who decide on aviation safety as they try to apply new rules to avoid the en masse shutdown of airspace last year.
Budget airline Ryanair was again vocal in its criticism and airline association IATA said more coordination was needed.
In Iceland, volcano experts had good news for airlines as they said the eruption was petering out.
"The eruption is nearing its death throes. It's not over yet, but it's dying," geophysicist Bjorn Oddson told local news portal Visir.
For Wednesday, Eurocontrol, the Brussels-based agency responsible for some of the world's busiest air corridors, said forecasts showed the ash cloud may affect parts of Denmark, southern Norway and southwest Sweden.
"This would have some impact on flights," it said. Its Twitter feed said new forecasts showed "no fly zone limited to south DK (Denmark), north DE (Germany) and partly Iceland."
Germany's meteorological service warned that the ash cloud could cause temporary airport closures in Hamburg and Bremen from midnight, and later possibly Berlin.
Traffic in Scotland and northern England was the main ash victim on Monday, but Britain said it thought this would ease. UK air traffic control body NATS said ash was expected over Britain from the early hours of Wednesday.
"At the moment we think Glasgow and Edinburgh will be affected throughout this afternoon but should be returning to normal tomorrow morning," British Transport Secretary Philip Hammond told BBC TV.
Among travelers affected were U.S. President Barack Obama, who left Ireland for Britain late on Monday ahead of schedule.
The Barcelona soccer team flew to London early for Saturday's Champions League final against Manchester United.
NEW RULES STILL IMPERFECT
Eurocontrol said the around 500 flights canceled on Tuesday were out of the about 29,000 expected that day.
But the new procedures that lie behind the avoidance of a shutdown of airspace put the onus on airlines to make judgments on whether it is safe to fly through ash, in coordination with the forecasting authorities and civil aviation bodies.
Showing the problems, sources told Reuters that a British research plane designed to sample ash remained grounded for a second day in a wrangle over its deployment.
The rules are also not accepted by all, with Germany backing a tougher stance for the sake of safety, aviation sources said.
"The potential for a patchwork of inconsistent state decisions on airspace management still exists ...," IATA director general Giovanni Bisignani said in a statement.
Ryanair said it had safely sent two planes into what authorities had deemed high ash zones over Scotland.
"You have to ask why a combination of bureaucratic incompetence in the CAA (Civil Aviation Authority) and the Met Office last night shut the skies over Scotland ...," Ryanair chief Michael O'Leary told BBC television.
Technically, Britain and Ireland have ruled out closing their airspace for now but the new rules only give pilots discretion to fly through the worst-risk areas if airlines had submitted an approved safety case, which the CAA said none had.
WORST OF ERUPTION OVER
In Norway, helicopter services to North Sea oil operations faced problems. Denmark shut a small area of its airspace.
After being warned that ash could reach western France, the French aviation authority said in a statement it was "very optimistic" about the coming days, with French airspace only very marginally affected.
French President Nicolas Sarkozy is due to host Obama and other G8 leaders in northern France this week.
Met Office meteorologist Halldor Bjornsson told Reuters that the signs of less activity were the fact that radar showed the ash plume was down to 5 km or less and that seismic data measuring eruptions also showed a tailing off.
"It all fits in with the same picture that the worst of this eruption is over," he told Reuters.
He said the ash now drifting over Europe was the ash from the powerful, first stage of the eruption and that the current height of the plume meant no new ash was feeding the cloud.
Grimsvotn erupted on Saturday and smoke belched as high as 20 km (12 miles) into the sky.
The eruption is the volcano's most powerful since 1873 and stronger than the volcano that caused trouble last year.
(Writing by Patrick Lannin, Simon Johnson, Tim Hepher; additional reporting by Carmel Crimmins and Conor Humphrey in Dublin, Philip Blenkinsop in Brussels, Oslo newsroom, Mette Fraende in Copenhagen and Niklas Pollard in Stockholm; Editing by Sonya Hepinstall/Maria Golovnina)
