Commercial aircraft slowly began to make their way into European skies Monday, after dangerous ash from a volcano in Iceland led to days of flight cancellations and delays.

Three KLM flights left Schiphol airport in Amsterdam Monday evening headed for New York, Dubai and Shanghai.

But mere hours after European officials devised a plan to get more planes off the ground Tuesday, British officials warned that the volcano's eruption has strengthened, sending even more ash toward Britain.

The British National Air Traffic Service announced Monday night that while airspace over Scotland will reopen Tuesday morning, it is unclear how much of England's may reopen. The service said should English airspace open Tuesday afternoon as planned, it may not extend to London.

Millions of passengers have been affected by flight delays since the Eyjafjallajokull volcano erupted in Iceland last Wednesday, spewing ash into the skies.

Volcanic ash poses a hazard for airplanes, as it can be sucked into jet engines where it can melt and then solidify. It also can cause visibility problems for pilots.

The resulting ash cloud has grounded tens of thousands of flights, with less than one-third of Europe's scheduled 28,000 flights taking off on Monday. The log-jam has left travellers stranded around the world and airlines losing up to US$200 million every day.

After a videoconference meeting on Tuesday, European officials said they would carve the skies up into three distinct zones -- one that will remain a no-fly zone in the face of the ash cloud threat, a second that will be open to all flights and a third that will be available only to some.

EU Transport Commissioner Siim Kallas said "the decision increases air space available to air traffic. This is the final outcome."

By Tuesday morning, the EU expects to "see more planes starting to fly."

Prior to the announcement, several European countries were taking action to alleviate the problems for their citizens. Much of southern Europe was still operating flights on Monday, though the air space over four of five of Europe's busiest airports remained closed.

In Spain, all airports remained open Monday and the government offered to have the country temporarily act as the main European hub while the problem is sorted out.

Germany's aviation authorities allowed Lufthansa to fly 50 long-haul planes into the country, hauling a combined passenger load of 15,000 people. The planes will fly at a very low altitude to avoid problems with the ash cloud.

In Britain, Prime Minister Gordon Brown sent three war ships across the English Channel to bring home some 150,000 citizens, said CTV's London Bureau Chief Tom Kennedy, who was stranded in Berlin himself.

Back in Britain, many public services -- including the school system -- have suffered because so many Britons are missing from their jobs while they wait to come home. This has only heightened the pressure on the government to resolve the situation, Kennedy said.

"There is that talk that they may use the ships, but I can tell you there is absolutely no discrimination. Even the (chancellor) of Germany, Angela Merkel, came back from a trip to the United States and it took her 60 hours to get back here," Kennedy told CTV's Canada AM by telephone from Berlin.

Then there are the airlines, which raised concerns with the way European governments have handled the situation so far.

Willie Walsh, the chief executive of British Airways, spoke out Monday about the management of the crisis, the day after he rode a test flight over Europeans skies.

He said the airline has concluded that "the risk has been minimal" and he wants the government to get planes off the ground.

The test flight he boarded Sunday "provides fresh evidence that the current blanket restrictions on air space are unnecessary," he said.

Even the International Air Transport Association chimed in on the way the issue was being handled by European leaders.

"It's embarrassing, and a European mess," Giovanni Bisignani, the IATA's chief executive, said Monday.

"It took five days to organize a conference call with the ministers of transport and we are losing $200 million per day (and) 750,000 passengers are stranded all over. Does it make sense?"

Some European airlines sought compensation for the major money they are losing on a daily basis, with some in jeopardy of going under if the air travel shutdown persists.

"There are several smaller airlines, we are told, that are on the brink of bankruptcy because of this," Kennedy said.

With files from The Associated Press