Several airports have reopened and flights taken to the skies as a blanket ban on flights is slowly lifted across Europe.

German airspace is officially closed until at least 8 p.m. local time, however Lufthansa and Air Berlin have taken advantage of special permission from DFS, Germany's aviation authority, to operate flights using visual flight rules. German flag carrier Lufthansa said that on Tuesday it planned to operate 200 flights, which is less than 15 per cent of its normal schedule.

Using DFS permission the airlines flew underneath the ash cloud, without full air-traffic control to reach stranded passengers. Hundreds of German tourists who had been stranded abroad for days have already arrived back in Frankfurt.

In Paris, the city's two largest airports, Orly and Charles de Gaulle are open for three-quarters of their scheduled flights, according to a French government minister.

Elsewhere in Europe, airspace in Austria, Switzerland, Bulgaria, Italy and the Netherlands has reopened.

Blanket of cloud remains

Flight restrictions have stayed in places where the volcanic ash cloud still poses a greater problem to aircraft.

Britain's national air traffic control body warned on Monday night that a new ash cloud was spreading south and east from Iceland's volcanic eruption, threatening further delays and closures.

Some flights in Scotland have resumed, however the airspace over London looked unlikely to open on Tuesday evening as planned.

British Airways have cancelled all short-haul flights but in a statement said they "hoped" they would be back in business by 3 p.m local time on Wednesday.

Concerns over visual flight rules

The German pilots' union Cockpit has said they have security concerns about the gradual return of flight traffic.

Cockpit spokesperson Jorg Handwerg told German public television station ARD that in this situation, the possibility of incidents occurring could not be completely ruled out. On the other hand, "pilots feel pressured because they feel that they have a responsibility to their employer."

Handwerg also said there were concerns that because the low altitude flights with visual flight rules had been given special permission, if anything was to go wrong in the air, pilots would be blamed.

German Transport Minister Peter Ramsauer defended the decision to allow flights to resume, saying it was "responsible" and "not a knee-jerk reaction".

"We have a good grounding in the regulations and all the data we have so that we know in certain zones, controlled flights are possible," he told public television station ZDF.

Pressure from airlines

Scientists from the German Aerospace Center (DLR) on Monday sent up a special plane outfitted with a laser in an attempt to measure the amount of volcanic ash in German airspace. The plane spent about four hours criss-crossing the country, and results are expected in the next few hours.

Air France, British Airways, KLM and Lufthansa reported no problems from their own test flights, though a senior US military official said the ash had caused some engine damage to one of NATO's F-16 fighter planes.

Grounded airlines are losing as much as 200 million euros (270 million dollars) per day, according to the International Air Transport Association. The European Commission said on Monday it was considering giving financial state aid to affected airlines.

cb/cmk/AFP/AP/dpa/Reuters
Editor: Chuck Penfold