Air passengers have been grounded across Britain and parts of northern Europe after ash clouds from an Icelandic volcano eruption drifted across the continent, closing a swathe of airports.
Hundreds of flights in the UK, Ireland and Nordic countries were cancelled and all British airspace north of London was closed on Thursday.
Airports in Scotland and London were shut, while flights to and from Manchester, Liverpool, Newcastle and Birmingham also faced disruption.
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British Airways said the plume of volcanic ash was severely affecting all airlines' flight activity.
"All airlines will be impacted and we will therefore not be able to operate services after 11.30am (2030 AEST) from London Heathrow, London Gatwick and London City," BA said in a statement on its website.
"Additionally, all British Airways domestic services have been cancelled on Thursday 15 April."
Passengers were being advised to contact their airlines before travelling.
Hundreds of flights affected
More than 150 flights to and from Heathrow and 108 flights to and from Gatwick, including many transatlantic services, were cancelled, and Aberdeen, Edinburgh and Glasgow airports were shut.
Airport operator BAA said: "Following advice from the Met Office, the National Air Traffic Service (NATS) has introduced restrictions to UK airspace this morning as a result of volcanic ash drifting across the United Kingdom from Iceland."
In northern Sweden all air traffic was suspended, as were flights in northern Finland.
Norway's King Harald V and Queen Sonja - who had planned to fly to Copenhagen for the Danish queen's 70th birthday - were
considering alternative transport options after Norwegian airspace was closed.
Particles could jam engines
Experts warned that the tiny particles of rock, glass and sand contained in the ash cloud would be sufficient to jam aircraft engines.
The European air safety body, Eurocontrol, said the cloud of ash was expected to move through northern Britain by 1300 GMT (2200 AEST).
Met Office forecaster Philip Avery said the ash, which was too high to affect people on the ground, could take several days to clear.
"NATS has good cause to be very cautious about this because in about 1982 a British Airways jumbo had the unnerving experience of having all four engines shut down as it flew through a plume of volcanic ash," he said.
A NATS spokesman told the BBC the ash cloud would move across Europe.
"The Volcanic Ash Advisory Centre has issued a forecast that the ash cloud from the volcanic eruption in Iceland will track over Europe tonight," he said.
"NATS is working with Eurocontrol and our colleagues in Europe's other air navigation service providers to take the appropriate action to ensure safety in accordance with international aviation policy."
An Australian man planning to return home to Perth from Edinburgh said he and his family had been told to expect a long delay.
"We were due to fly out this morning and head back to Perth, but now we've been delayed three days," he told Sky News.
"We've been up in St Andrews so we'll probably head back up there and see some friends and extend our holiday."
The eruption under a glacier in the Eyjafjallajoekull area of Iceland is the second in the country in less than a month.
