Flights ease Europe's air traffic crisis; Volcano ash continuing to blow towards Britian

London, England - Half of all Europe's flights were back in the air Tuesday, but more ash from Iceland's erupting volcano threatened to stall plans to reopen British airspace.

Although authorities in Iceland reported that eruptions from the Eyjafjallajokull volcano were weakening, volcanic ash already in the air continued to blow towards Britain.

The country's weather forecaster, the Met Office, said current wind patterns suggested no let up until the end of the week.

"At the moment current weather conditions aren't set to change until about Friday and then it looks like then the change is going to be south-westerly winds which will then take it away from the UK," a spokeswoman told CNN.

About 14,000 flights were expected to operate in European airspace Tuesday -- half of scheduled air traffic, according to Eurocontrol, the intergovernmental body that manages European air travel.

Flights were restricted to those above 20,000 feet, Eurocontrol said. Lower air space is closed or severely restricted across Europe, it added.

Flights were back in the air in France and Germany. Around 75 percent of scheduled flights were expected frome Franc's two main airports, Charles de Gaulle and Orly, French Minister for Ecology Jean-Louis Borloo told French radio network RTL.

Germany's air authority, DFS allowed flights to take off and land in German airports at low altitude under visual flight rules to reduce the risk of damage to airline instruments. The country's main carrier Lufthansa said it hoped to operate as many as 330 flights, including some long-haul flights, Tuesday.

Some countries opened their airspace to travel, while keeping airports closed. Flights higher than around 20,000 feet were allowed through Danish airspace, the country's air traffic control service NAVIAIR said.

Norway opened its part of its airspace near Bergen briefly on Tuesday and predicted Gardermoen, just north of Oslo, would be open all day, the country's air traffic control service AVINOR said.

Meanwhile Finland confirmed all Finnish airports would remain closed until 9 a.m. local time (1 a.m. ET) Wednesday.

While some traffic was moving, air authorities across Europe remained cautious about predicting relief for thousands of travelers still stranded abroad six days after Iceland's Eyjafjallajokull volcano spewed potentially dangerous volcanic ash into the sky.

Authorities warned that Tuesday's partial reopening would not bring air traffic to its usual levels. European Union officials agreed to a plan involving three zones: one that remains closed, one open to all flights and one open only to certain flights from Tuesday morning.

There will not be "any compromise on safety," European Transport Commissioner Siim Kallas said Monday. He called the current situation "unsustainable" and said it is clear "we cannot just wait until this ash cloud dissipates."

Kallas rejected suggestions that European Union ministers should have acted more quickly to allow flights to resume. It took Sunday's test flights to provide the information necessary, he said.

Since the volcanic eruption worsened last week, sending an ash cloud into the skies, airlines have been losing at least $200 million a day, according to the International Air Transport Association, the trade group representing airlines. Airports had lost close to 136 million euros ($184 million) as of Sunday, said Olivier Jankovec, director general of Airports Council International, Europe.

More than 6.8 million passengers have been affected, Jankovec said in a statement, adding that the effect is worse than after the September 11 terrorist attacks on the United States.

Thousands of people have been living in airports.

"I have been living out of my carry-on for five days," said Paulo Wu, stranded in Amsterdam, Netherlands. After two nights sleeping on a cot at the airport, he was able to get into a hotel with an actual bed, he said. "I have no bags. My bags are somewhere, I think, at the airport. I just have my carry-on," he said.

Britain dispatched Royal Navy ships to bring home some stranded British travelers, including members of its military, Prime Minister Gordon Brown said Monday.

The British Royal Navy's HMS Albion picked up 300 civilians along with hundreds of British military personnel when it arrived Tuesday in Santander, Spain. The military members are on their way home from Afghanistan, Britain's Ministry of Defence has said.

British Airways said it had canceled all short-haul flights for Tuesday. The airline said it was still hoping to operate longhaul flights scheduled to depart after 4 p.m. (11 a.m. ET), but it was subject to the "full and permanent opening" of airspace.

A British Airways test Sunday found no damage to the aircraft at a variety of altitudes, the airline said in a statement Monday.

"The analysis we have done so far, alongside that from other airlines' trial flights, provides fresh evidence that the current blanket restrictions on airspace are unnecessary," said Willie Walsh, British Airways' chief executive.

Finland's Ministry of Defense, however, said in a statement Monday that Finnish Air Force F-18 Hornet fighters that conducted test flights over northern Finland on Thursday showed effects from volcanic material.

"A post-landing inspection revealed accumulations of powdery volcanic dust in the aircraft's air intakes," the ministry said. Officials used a fiberscope to closely examine the engines of one aircraft, and "imagery ... indicated that even a short-duration flight inside an ash cloud may cause substantial damage to aircraft engines."

The engines will undergo a more thorough inspection, the ministry said.

Meteorologist Derrick Ryall of the MET Office in London said there is no "defined safe limit" for volcanic ash.

"No one has said what a safe limit for aircraft is, so therefore it's very difficult for these judgments to be made," he said.

The air disruptions have led to cancellations of numerous high-profile visits. Many world leaders, including President Obama, were unable to attend Sunday's funeral services for Polish President Lech Kaczynski.

U.S. Secretary of State Hillary Clinton canceled plans to travel to Helsinki, Finland, a State Department official said. Clinton was set to depart Washington on Tuesday. No decision has been made about whether she will keep plans to visit Tallinn, Estonia, the official said. If she does, she will not depart before Wednesday.

CNN