The Icelandic volcano which disrupted hundreds of flights in northern Europe is no longer spewing out ash and the eruption seems to have halted, weather officials said on Wednesday.
Two German airports halted flights on Wednesday after the ash, which began bursting from the Grimsvotn volcano on Saturday, drifted south into European air routes.
However, air traffic across much of the region started to return to normal.
"Plume not visible on radar. Awaiting confirmation that eruption has ceased," said an advisory note to airlines on the website of the British meteorological office. "Eruption may have ceased at 0200," it added.
"There are indications that it's ceasing really. There's no plume detected since 0300 GMT and the last plume was around 0210 and since then there seems to be mainly steam coming from the crater," Icelandic meterologist Hrafn Gudmundsson told Reuters.
"It is not officially declared over. We have every indication that it's been ceasing," he added, saying it was up to geophysists to formally declare it over.
The eruption of Grimsvotn forced the cancellation of 500 European flights on Tuesday, with Scotland especially hard hit. In northern Germany, Hamburg and Bremen airports cancelled takeoffs and landings, and German authorities said Berlin terminals could also face closure from 1000 GMT.
"Currently there is no forecast when the restriction will be lifted," Hamburg airport said on its website.
Grimsvotn erupted on Saturday and smoke belched as high as 20 km (12 miles) into the sky.
The eruption is its most powerful since 1873 and stronger than the volcano that caused trouble last year. Signs the power of the volcano was diminishing came already late on Tuesday.
While the ash has disrupted travel plans, including the state visit of US President Barak Obama to Ireland, it has not created the kind of chaos caused by an Icelandic volcano last year when more than 10 million people were hit by a six-day European airspace shutdown.
That cost airlines $1.7 billion.
But the eruption has exposed disarray among the authorities who decide on aviation safety as they try to apply new rules to avoid another mass closure of European airspace.
New procedures 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.
Highlighting 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.
British airport operator BAA, majority owned by Spanish infrastructure group Ferrovial, warned some flights would continue to be affected. But it said flights were expected to resume at Glasgow Airport Wednesday morning, and it expected a "fuller programme" of services at Edinburgh.
In Scandinvia, traffic was mostly normal after some disruptions on Tuesday.