bbc news in the uk.
restrictions on uk airspace have been extended until 0100 bst on sunday, as the danger to planes from volcanic ash from iceland persists.
The uk's national air traffic service (nats) said some domestic flights may be able to take off from scotland and northern ireland before 0100.
But british airways said all short-haul flights to and from heathrow and gatwick on sunday have been cancelled.
Officials warn that european airspace could be disrupted for several days.
Nats said the ash cloud was "moving around and changing shape", and some domestic flights may be able to take off from scotland and northern ireland if it "moves sufficiently".
Prof brian golding, head of forecasting research at the met office said: "the latest information we have suggests the ash will remain over the uk for several days.
"we need a change of wind direction that stays changed for several days and there is no sign of that in the immediate future," he added.
Restrictions had been lifted in scotland and northern ireland on friday evening but were reapplied overnight
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Hundreds of thousands of passengers have been stranded in the uk and abroad by flight cancellations.
"current forecasts show that the situation is worsening throughout saturday," said nats, adding that it was "most unlikely" that many flights would operate later.
It said anyone hoping to travel should contact their airline before travelling to the airport.
A further update from nats is expected at about 1500 bst.
Restrictions on flights in the uk have been in place since 1200 bst on thursday because of fears particles in the ash from the volcanic eruption in iceland could shut down plane engines.
Air travel across europe has been severely affected, with a range of countries from belgium to switzerland completely closing their airspace.
In other developments:
ryanair cancelled all flights to and from northern europe until 1300 bst on monday. It will keep running in southern and central europe, although flight restrictions are being imposed in hungary and romania
p&o ferries said it had dealt with 30,000 calls on friday - the most it had dealt with on one day in its history. It said it would be unable to accept any further foot-passenger bookings
eurostar trains reported a complete sell-out of its services to brussels and paris for the second day on friday. Its trains are fully booked until monday.
german airline lufthansa has cancelled all its flights until 2000 local german time (1900 bst)
unable to catch flights, many commuters across northern europe have sought other means of transport, which has seen people filling trains, buses and ferries.
Uk-based aaron soni is among those affected. He had been visiting his parents in melbourne, australia, with his wife and son.
Mr soni - who was due to return to the uk on saturday but was told not to bother checking with his airline until thursday - said his, and his wife's, work commitments are "in chaos" and their son had been due to return to school on monday.
"it's getting expensive to pay all the bills," he said.
The no-fly zone also means some world leaders might have difficulty attending the funeral of the polish president on sunday.
And celebrities have not been immune to the travel disruption.
Us singer whitney houston had to take a car ferry from britain to ireland for a concert in dublin and comedian john cleese reportedly paid $5,100 (£3,319) for a taxi ride from oslo to brussels.
The ministry of defence (mod) said it was also affected by the restrictions.
An mod spokeswoman said: "we are under the same restrictions as everybody else, above 3,000 ft. Below 3,000 ft essential helicopter operations, such as search and rescue operations, have resumed."
manchester and liverpool airports had been offered a six-hour window - between 0400 bst and 1000 bst - in which to operate some flights, but the changing conditions meant that was later revoked.
Baa said passengers due to fly should not go to its airports - heathrow, stansted, southampton, edinburgh, aberdeen and glasgow - but should contact their airline for re-ticketing information.
Bbc weather forecaster nick miller said: "as the weekend goes on there is a risk that prevailing winds will keep volcanic ash in the air above parts of the uk, and may even bring it back to those parts from which it has cleared."
european air traffic control organisation eurocontrol said more than half of the normal 300 trans-atlantic flights had also been cancelled and it warned of "significant disruption" of european air traffic on saturday
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The civil air navigation services organisation (canso), a global association of air traffic control companies, said the knock-on effect of the cancellations so far would probably disrupt european airspace for several days.
Experts say the tiny particles of rock, glass and sand contained in the ash cloud could jam aircraft engines, as has happened in previous incidents of planes flying into plumes of volcanic ash.
The last eruption of the eyjafjallajoekull volcano system that is creating the problems was on 20 march, when a 0.5km-long fissure opened up on the eastern side of the glacier at the fimmvoerduhals pass.
The eruption prior to that started in 1821 and continued intermittently for more than a year.
our tv, is reporting major disruption to wednesday and then ten days to get thnigs back to normal.
And bought 
So, ASSUMING, and there is a lot of that going on in this debate 
getting to Dover is an issue, DCL will either get it done or we go NEXT year! 
I'd say 8:15-8:30pm since that's what time they currently begin on the other itineraries.
