UK officials are to open air space in Scotland from 7 am on Tuesday and later in the day in England and Wales, in the first sign that the chaos that has stranded hundreds of thousands of travellers around the world may be easing.

The Icelandic volcano that prompted the disruption has stopped emitting ash the National Air Traffic Services agency said on Monday. “Assuming there are no further significant ash emissions we are now looking at a continuously improving situation, Nats said.

However, officials said it was not clear if the window of clear air space that was opening up would last for 24 hours or several days at this stage.

“This is a dynamic and changing situation and is therefore difficult to forecast beyond 7 am local time,” Nats said, advising that it was now up to airlines and airports how they used the temporary lifting of the restrictions that have paralysed three of the world’s busiest international airports, including Heathrow, for five days.

A UK government source said that under the “gloomy” scenario of the volcano erupting again officials would press ahead with alternative plans such as using Madrid as a transport hub, using coaches, boats and trains to ferry people from the Spanish capital to the UK.

There will be a further meeting of Cobra, the British government’s emergency panel, later on Monday.

Earlier the UK started to send Royal Navy ships to help rescue thousands of British travellers stranded around Europe, in the most dramatic official response so far to the closure of airspace by volcanic ash from Iceland.

“I expect HMS Ocean to be in the Channel today. I expect Ark Royal to be moving towards a Channel port,” Gordon Brown, the prime minister, told reporters in London on Monday. “Our first priority is to avoid the inconvenience being caused to thousands of people.”

As the Icelandic volcano continued to erupt, sending ash three km into the sky, a Met office spokesman confirmed that the cloud of ash fragments that have brought much of Europe to a standstill was expected to reach the east coast of Canada around noon London time. A UK Met Office spokesman said there was no indication yet that the cloud would affect US airspace.

Canadian airlines were reviewing flight schedules to and from Newfoundland on Monday morning in the wake of the weather reports.

Such disruptions would be the first in North America affected by the volcano. Newfoundland, Canada’s most easterly province, is 2,500 km from Iceland, roughly the same distance as eastern Germany.

Several airlines cancelled flights on Sunday night and early Monday morning, but an official at St John’s international airport told the Financial Times that all the cancellations so far had been due to fog. Air Canada warned on its website that flights to St John’s as well as Gander and Deer Lake “may be impacted by volcanic activity”.

Environment Canada said early on Monday that there was “a low probability of risk” from volcanic ash “as satellite imagery does not support ash presence in high concentrations”.

The Met’s most recent forecasts show that the winds that have been pushing the ash cloud south over Europe from Iceland will not start to change direction until the end of this week.

“If the volcano keeps emitting ash and the wind keeps blowing it down, there is a risk of further ash over the UK.” the spokesman said.

European authorities were facing growing pressure to lift airspace restrictions as the airlines industry body warned that the volcanic ash cloud’s impact on their business was worse than that of the 9/11 terror attacks.

The authorities were set to keep large parts of the continent a no-fly zone for a fifth day even after airlines announced on Sunday they had carried out test flights that landed safely.

European Union transport ministers were due to discuss the crisis in a video conference called by Spain in its capacity as the 27-nation bloc’s president. Officials in France and the UK said they were studying results of flight tests from Lufthansa, Europe’s biggest airline group, KLM and other airlines that conducted more than a dozen flights during the weekend without incident.

As officials said weather conditions showed no signs of dispersing the volcano ash drifting across the continent, some carriers warned European Commission officials in Brussels that there could be airline bankruptcies.

Giovanni Bisignani, head of the International Air Travel Association, estimated airline revenue losses were reaching $250m a day, up from an estimate of $200m on Friday. Mr Bisignani called for urgent action to reopen airspace safely and called for a meeting of the International Civil Aviation Organisation, the United Nations aviation body.

“This volcano has crippled the aviation sector, firstly in Europe and is now having worldwide implications. The scale of the economic impact [on aviation] is now greater than 9/11 when US airspace was closed for three days,” Mr Bisignani said, referring to the September 11 2001 attacks.

“We must move away from this blanket closure and find ways to flexibly open air space, step by step,” he told a news briefing in Paris.

Speaking ahead of the EU talks, Siim Kallas, transport commissioner, said: “We cannot just wait until this ash cloud dissipates.”

Hundreds of thousands of travellers have been marooned around the world since Thursday, when authorities imposed flight restrictions amid fears that aircraft engines would be choked by ash from Iceland’s Eyjafjallajökull volcano.

Lufthansa, which says it is losing €25m ($34m, £22m) a day from the crisis, said it was “scandalous” for authorities to have imposed the ban on what appeared to be limited data from computer images, rather than safety test flights.

Dubai’s Emirates airline said it was losing $10m a day, in part because of the accommodation and meals it was providing for about 6,000 stranded passengers.

Additional reporting by Jim Pickard in London