The volcanic ash plume in Iceland and Glasgow's deserted airport terminal
All flights in and out of the UK and several other European countries have been suspended as ash from a volcanic eruption in Iceland moves south.
Up to 4,000 flights are being cancelled with airspace closed in Norway, Sweden, Finland and Denmark among others.
The UK's air traffic control service (Nats) said no flights would be allowed in UK airspace until at least 0700 BST on Friday amid fears of engine damage.
Safety group Eurocontrol said the problem could persist for 48 hours.
The volcano is still spewing ash and the wind direction is expected to continue bringing clouds into UK and European airspace for some time to come.
Republic of Ireland
Partial or planned closures:
Sweden (total closure by 2000 GMT)
France (two main Paris airports plus several in the north)
Denmark (total by 1600 GMT)
Finland (northern airspace closed till 1200 GMT Friday)
Belgium (total from 1430 GMT)
Netherlands (being shut progressively)
The UK's airspace restriction was the worst in living memory, a Nats spokesman said. Some 600,000 people are thought to have been affected.
Nats suggested that the restrictions were unlikely to be lifted after 0700, saying it was "very unlikely that the situation over England will improve in the foreseeable future".
Passengers were advised to contact their carriers prior to travel.
Transport Secretary Lord Adonis said he was "closely monitoring the situation" and would be meeting with key transport officials on Friday morning.
Experts have warned that the tiny particles of rock, glass and sand contained in the ash cloud from the still-erupting volcano could be sufficient to jam aircraft engines.
By David Shukman
BBC environment correspondent
A lone plane is in the skies above Britain tonight on a research mission to investigate the volcanic plume.
The aircraft - with scientists on board - is taking measurements of the height, density and position of the ash.
There are limits to what satellites and ground observations can discern about the plume.
Its flight path was planned to take it from Oxford to Prestwick to Lossiemouth to Newcastle and then back south.
Among the researchers on board are specialists in atmospheric science.
The aircraft - a Dornier 228 - is managed by the government-funded Natural Environment Research Council. Its head of airborne research, Peter Purcell, described the plane as "extremely adaptable and capable".
"The instrumentation will allow the crew to safely monitor the atmospheric conditions as the plume is approached," he said.
The findings will be fed to Met Office to help improve forecasts for the plume's position.
The Health Protection Agency said the ash from the Eyjafjallajoekull eruption did not pose a significant risk to public health because of its high altitude.
However, the British Lung Foundation has warned people with lung conditions to keep their medication with them as a precautionary measure.
These are some of the knock-on effects:
Eurocontrol says Germany is monitoring the situation and considering partial airspace closures
The two main airports in Paris and many others in the north of France are closing
There is severe disruption in France and Spain, where all northbound flights are cancelled
Nats is due to make an announcement shortly as to the arrangements that will be in place through to 1300 BST on Friday
British Airways offers refunds or an option to rebook after all its domestic flights are suspended
Flybe announces it has cancelled all flights up until 1300BST on Friday and more than 25 services due to run after that.
A spokesman for Nats, which was formerly known as the National Air Traffic Services, said: "The Volcanic Ash Advisory Centre has issued a forecast that the ash cloud from the volcanic eruption in Iceland will track over Europe tonight.
"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."
The European air safety body, Eurocontrol, said the cloud of ash had reached 55,000ft and was expected to move through northern UK and Scotland.
Brian Flynn, assistant head of operations of its central flow management unit, told the BBC: "As it moves toward the Netherlands and Belgium it will dissipate and lose intensity, like any weather phenomenon. But we don't know what the extent of it will be."
The Natural Environment Research Council (NERC) has sent up a reconnaissance flight to investigate how the ash is distributed in the cloud, something that is impossible to assess from satellite imagery.
Dr Mike Branney, senior lecturer in volcanology, University of Leicester, said: "Volcanic ash is not good to plane engines.
"Firstly it is highly abrasive and can scour and damage moving parts. Secondly, if it enters a jet engine the intense heat of the engine can fuse it to the interior of the engine with a caking of hot glass, which ultimately can cause the engine to cut out completely.
"This is a sensible precaution."
In 1982 a British Airways jumbo had all four of its engines shut down as it flew through a plume of volcanic ash.
There was also an incident on 15 December 1989 when KLM Flight 867, a B747-400 from Amsterdam to Anchorage, Alaska, flew into the plume of the erupting Mount Redoubt, causing all four engines to fail.
Once the flight cleared the ash cloud, the crew was able to restart each engine and then make a safe landing at Anchorage, but the aircraft was substantially damaged.
A BAA spokesman said: "Passengers intending to fly today are asked to contact their airline for further information."
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