A new ash cloud threatened to disrupt plans to reopen some of Britain's airspace last night. The air traffic control service Nats said it was spreading south and east towards the UK.
Scottish airspace was nonetheless expected to be available from 7am this morning with more airspace over England becoming available from 1pm, though not as far south as London's airports. Manchester airport said it hoped to be open from 9am. The situation for Northern Ireland's airports was uncertain.
"The volcano eruption in Iceland has strengthened and a new ash cloud is spreading south and east towards the UK," Nats said in a statement last night. "This demonstrates the dynamic and rapidly changing conditions in which we are working. Latest information from the Met Office shows that the situation is worsening in some areas."
Nats said it would provide further updates at 3am and 7am this morning. British Airways had been aiming to resume some flights from London's airports from 7pm today, but because of the new developments, a BA spokesman said it was "reviewing" its schedule.
Earlier the airlines had been putting heavy pressure on the Government to lift the ban, pointing to the results from test flights and suggesting that the complete closure of UK airspace was an over-reaction.
Even before Nats' latest warnings, aviation experts remained uncertain as whether it was too early to lift restrictions on airspace. There were concerns that any amount of particles still threatened problems.
Chris Yates, an aviation consultant, said the position of the expert International Airways Volcanic Watch Operations Group was that there was "no definition of a safe concentration of ash" as a result of more than 80 jet incidents between 1980 and 2000.
"While it remains possible to find clear air high above us, this doesn't necessarily mean there are no pockets of high concentrations of ash at the various flight levels," Mr Yates said. "I would therefore suggest it's better to err on the side of caution."
Ben Vogel, editor of Jane's Airport Review, pointed out that engine problems caused to two Finnish Air Force F-18 fighter-bombers last week – disclosed by Nato yesterday – underlined the damage that volcanic dust could do to planes, but said the "small risk" had to be balanced against the financial damage to the airline industry.
According to analysts at UBS, airlines have been losing €140m (£123m) a day, with no insurance cover available to protect them. The no-frills airline easyJet put its total losses at £40m, while British Airways revealed it was losing up to £20m a day, making total losses of about £100m.
BA and other airlines lobbying to be allowed to restart operations ran a series of "test flights" to show that the skies were safe while also holding talks with plane and aero-engine manufacturers about the risk posed by particles from the ash cloud.
Analysis of a BA test flight over the Atlantic on Sunday, which took off from Heathrow and landed at Cardiff, had revealed no variations in the aircraft's normal operational performance, the airline said.
BA's chief executive Willie Walsh, who joined a flight crew on board a Boeing 747, said: "The analysis we have done so far, alongside that from other airlines' trial flights, provides fresh evidence that the current blanket restrictions on airspace are unnecessary. We believe airlines are best positioned to assess all available information and determine what, if any, risk exists to aircraft, crew and passengers."
The no-fly zone was imposed across Britain on Thursday after a plume of ash shot into the air south of Iceland on Wednesday night. Even with some flights returning, there is not expected to be any rapid improvement in the situation of the 500,000 British passengers left without flights at home and abroad. It is expected to take airlines at least a week before they ferry back those stuck abroad and begin operating a full service.
A new £500m cruise ship, the Celebrity Eclipse, is to sail to Spain to pick up almost 3,000 stranded British tourists. The luxury vessel has delayed its inaugural celebration and is due to leave Southampton tonight for Bilbao.
In the meantime, travellers have continued to make their way back on congested ferries and Eurostar trains. All ferry services between Spain and the UK are fully booked for a week.
The Government decided to call in the Navy after the Prime Minister chaired a meeting of Cobra, the emergency planning committee. There are plans for three warships to help with the rescue effort.
HMS Albion, an amphibious landing ship, was already on its way to Santander in northern Spain to pick up soldiers returning from Afghanistan, and will now be available to take civilian passengers as well. HMS Ark Royal and HMS Ocean, aircraft and helicopter carriers, are on their way down to continental waters, with their destinations still being planned.
Some passengers complained that they had received little consular assistance, despite the Government's whirl of activity. Some passengers also contacted the Air Transport Users Council complaining that airlines were refusing to meet the terms of EU legislation requiring them to pay for hotel and living expenses for passengers whose flights had been cancelled.
Airlines, whose shares have slumped, have appealed for government compensation to help them to recover from the unprecedented shutdown. Economists at Grant Thornton have estimated that the loss of productivity will cost the economy around £10m a day as business people are unable to travel.
In Britain, the number of schoolchildren stuck abroad prompted an exams body, the Joint Council for Qualifications, to consider delaying GCSE papers. At St Mary's Calne, an independent girls' school in Wiltshire, where 45 of the 300 pupils are stranded overseas, GCSE German oral exams were cancelled.
But the flight ban is not bad news for everyone: hoteliers in the Lake District have reported a surge in bookings. The tourism body Visit Britain said the airline industry's problems could prove lucrative for local tourism businesses and the UK economy.
As flights begin to return, airports warned passengers to check with airlines before setting off. A spokesman for Glasgow airport said: "We strongly advise passengers to check the status of their flight before travelling to the airport, as not all flights will operate. All Scottish airports are currently working with airlines to understand their intentions in terms of operating flights."
A Heathrow airport spokesman said: "As things stand, all flights remain suspended. When airports do open for business, we will continue to strongly advise passengers that they must check the status of their flight with airlines before travelling to airports."
*Former prime minister Tony Blair has been unable to fly home from Israel, where he has been carrying out his role as a Middle East envoy. Cherie Blair said her husband was hoping to return home as soon as he could to help Labour win a historic fourth term.
*Rock band Status Quo will be forced to travel home from a gig in Moscow by rail and road after their flights were affected. Their tour bus has been dispatched to pick them up from Warsaw and the journey will take almost two days.
*Radio 1 DJ Chris Moyles was forced to miss his morning show after he was grounded in New York. He had been expected to return on Sunday. Moyles described his situation as "a very, very surreal [but] kind of pleasant nightmare", and said he had run out of underwear. "I'm going to have to get my pants and socks laundered at the hotel," he added. Fellow BBC DJ Scott Mills took his place on the breakfast show.
*Actor Kiefer Sutherland, who last week caused a stir after being thrown out of Stringfellows nightclub, has still not been able to fly home to California from London.
*Filming for the new series of the popular television show Dragons' Den has been delayed, with judge Peter Jones unable to return home from Barbados due to the travel chaos.
* Miley Cyrus is unable to attend the UK premiere of her new film The Last Song, and singer-songwriter Newton Faulkner is stranded in Hong Kong. The Cribs, Delphic and Gary Numan were also forced to pull out of the weekend's Coachella festival in California.
*US singers Usher and Adam Lambert are unable to carry out promotional duties in Europe, while actress Demi Moore has declared herself unable to attend UK press interviews for her new film The Joneses.
*And cast members of the stage version of Hi-de-Hi! must be wishing they'd gone camping rather than holidaying in France and the Maldives after two actors got stranded. Understudies will fill in for Peter Amory and Rebecca Bainbridge at the Haymarket in Basingstoke this week.