Aircraft grounded until Saturday
Flights across much of the UK have been grounded for a second day as volcanic ash from Iceland drifts across Europe, posing a potential threat to aircraft.
Air traffic control body Nats said airspace restrictions would be lifted in most of Scotland and Northern Ireland from 1900 BST on Friday.
But it extended restrictions on airspace in England and Wales until at least 0700 BST on Saturday.
European controllers said some 17,000 flights had been cancelled on Friday.
The partial lifting of Scottish restrictions on Friday will also cover Shetland and the Orkneys, and will also mean some North Atlantic traffic will be able to operate, Nats said.
A tiny number of services are being permitted elsewhere on Friday as the ash clears, mainly in and out of Northern Ireland, western Scotland and south-west England.
Two planes were able to fly in and one left Manchester by lunchtime on Friday.
Wind factor
Over the next 24 to 36 hours, prevailing winds will shift slightly to drive the central part of the ash plume further to the north toward Scandinavia, according to BBC weather forecaster Matt Taylor.
"However, later this weekend, they will return to a northwesterly direction and are more likely to bring the risk of ash back to the UK."
Although the winds can be predicted, the crucial factor is how much ash the still-erupting volcano is pumping into the atmosphere.
Hundreds of thousands of people have been stranded in the UK or abroad, many unable to return home as a result of the flight cancellations.
Kerry Stothart, of Maidstone, is stuck in Belgium after being redirected there on their way back from Atlanta.
She said: "We are a party of 10 people including four children, one diabetic, one with ADHD and Aspergers, and a blind lady. This is an absolute nightmare.
"We've had to pay £1,400 for a coach and ferry to take us back home, and that's not until 9pm."
The Norfolkline ferry service between Dover and Dunkirk said it had limited capacity for passengers both on foot and in cars on some crossings.
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 Health Protection Agency has stressed the ash does not pose a significant risk to public health, and Health Protection Scotland says only a low concentration of particles is expected to reach the ground.
It advises that some people with respiratory problems may experience short-term effects, but there should be no serious harm.
Nats initially restricted all UK airspace at 1200 BST on Thursday, but allowed some flights into Belfast, Prestwick and Glasgow airports as gaps in the cloud became apparent.
It said that a limited number of flights between Northern Ireland and the western isles of Scotland to and from Glasgow and Prestwick would continue until 1900 on Friday, as would North Atlantic traffic to and from Glasgow, Prestwick and Belfast.
Stranded passengers have flooded other modes of travel. Eurostar trains reported a complete sell-out of its services to Brussels and Paris for the second day on Friday.
"We are carrying more than 38,000 people today and all our trains are full," a spokeswoman for the company said.
"We are telling potential customers without bookings not to come to St Pancras because they will not be able to travel."
An RAF spokesman said 500 military personnel trying to get back to the UK from Afghanistan were stranded in a number of locations by the travel chaos.
Rail and ferry services are reporting rises in their passenger numbers, with ferry operators Stena and Fastnet saying there were significant increases in customers on services departing from Wales.
European air traffic control organisation Eurocontrol has said that the situation was "as bad as on Thursday or worse".
Eurocontrol spokesman Brian Flynn said that "we lost 8,000 flights of 28,000 on Thursday" and that more than 50% of normal passenger movement would be lost on Friday across Europe.
* Eurocontrol also say the volcanic ash cloud is extending in some places from the ground up as far as 35,000 feet
* The airspace of the Netherlands, Belgium, Denmark, Finland, the Czech Republic and Lithuania
# Northern parts of Germany, France and Poland are also fully restricted
# A small number of flights to and from the west are operating from airports at Dublin and Shannon in the Irish Republic and smaller airports in Sweden and Norway
# Polish officials will take a decision on Friday about delaying the state funeral of Polish President Lech Kaczynski,
# Shares in airlines BA, Air France, KLM and Lufthansa
The Nats extension of restrictions for the UK was the second since Thursday evening.
So far an estimated 600,000 passengers have been affected in the UK.
Transport Secretary Lord Adonis said he was "closely monitoring the situation" and would be meeting key transport officials.
He also said the volcanic ash cloud is expected to cause "significant disruption" to air services for at least the next 48 hours.
Although the Prince of Wales was still due to attend the funeral of the president of Poland Lech Kaczynski on Sunday, his wife, Camilla, the Duchess of Cornwall has had to cancel a visit to a Polish cultural centre in London, Clarence House has said.
The duchess was due to sign a condolence book for the late president but the disruption caused by the ash cloud meant she was unable to travel down from Scotland.
Mr Flynn told the BBC a lack of wind meant the ash cloud was "progressing very slowly eastwards" and remained "very dense".
Ash from the cloud was first detected at ground level on Scotland's Northern Isles on Thursday evening, and early reports from the Shetland islands said that the sky had a light yellow hue on Friday morning.
The Eyjafjallajoekull eruption was the second in Iceland in less than a month.
Volcanologist Thor Thordarsson said if the volcano maintained its current phase of activity, then the eruption could be over in "a few hours or even a few days" meaning the atmosphere would clear shortly afterwards.
But he added: "If the eruption has a phase change and starts to produce lava... then we might be in for a much longer haul, an eruption that might last for months or even years, with a quiet period in between intermittent explosions."
