Media playback is unsupported on your device Media caption Transport Secretary Philip Hammond warns of disruption ahead 
 
 Flights in and out of Scotland have been cancelled as a volcanic ash cloud from Iceland heads towards the UK. 
 
 BA, KLM, Easyjet, Flybe, Aer Lingus, Loganair and Eastern Airways have cancelled services on Tuesday, and some flights over the Atlantic were delayed. 
 
 The threat of further disruption led US President Barack Obama to fly out of the Republic of Ireland a day early to get to London for a state visit. 
 
 Ash from another Icelandic volcano led to huge disruption in Europe last year. 
 
 Air Force One 
 
 Mr Obama had been due to fly to the UK on Tuesday morning, but White House deputy press secretary Josh Earnest said the decision to bring his arrival forward had been taken "due to a recent change in the trajectory in the plume of volcanic ash". 
 
 The Met Office forecasts the ash cloud will reach northern and western Scotland overnight, and will clip northern parts of Northern Ireland early on Tuesday. None of England is likely to be affected. 
 
 A Met Office spokesman said it was difficult to forecast the cloud's direction beyond that because weather systems were changing so rapidly. 
 
 A number of airlines are choosing not to fly through Scottish airspace on Tuesday: 
 
 British Airways is not operating any flights between London and Scotland until 1400 BST 
 
 KLM cancelled flights to and from Aberdeen, Glasgow and Edinburgh, as well as some to Newcastle 
 
 EasyJet cancelled flights to and from Edinburgh, Glasgow, Inverness and Aberdeen scheduled for between 0500 and 0900 BST 
 
 Flybe cancelled flights to and from Aberdeen and Inverness 
 
 Aer Lingus cancelled a number of its flights between the Republic of Ireland and Edinburgh, Glasgow and Aberdeen 
 
 Glasgow-based Loganair has cancelled 36 flights. Only inter-island routes in Orkney are unaffected 
 
 Eastern Airways will not be operating any services in or out of Scottish airspace 
 
 Transport Secretary Philip Hammond told BBC Two's Newsnight that "most, if not all, flights into and out of Glasgow and Edinburgh and airports to the north will be stopped" on Tuesday morning. 
 
 But he said services should resume from Glasgow and Edinburgh by about lunchtime, and in other airports by Wednesday morning. Any disruption later in the week should be "limited", he added. 
 
 Earlier, Mr Hammond said there had already been "modest delays" to flights, particularly those crossing the Atlantic. 
 
 "Clearly, this is a natural phenomenon which we cannot control, but the UK is now much better prepared to deal with an ash eruption than last year." 
 
 A spokesman for Edinburgh Airport said it was anticipating disruption to many services on Tuesday. 
 
 In a statement on Monday evening, he said: "Only Ryanair is intending to operate a full service from Edinburgh Airport. Passengers should not travel to the airport without checking with their airline first regarding the status of their flight." 
 
 Andrew Haines, chief executive of the Civil Aviation Authority, said he hoped to avoid a repeat of last year's travel chaos, but he admitted it was still unclear how badly flights would be affected. 
 
 "We know so much more about the volcanoes. We have an improved model. 
 
 "We have better measuring equipment and we have better relationships with airlines so it should be much better but we're still at the hands of both the weather and the volcano; those are the two uncertainties." 
 
 Media playback is unsupported on your device Media caption Andrew Haines, of the CAA, said UK aviation had "learned a great deal" 
 
 Champions League finalists Barcelona are already considering bringing forward their flight to London ahead of Saturday's final at Wembley against Manchester United. 
 
 The Catalan club had originally planned to travel on Thursday. 
 
 "Let's see what they [the experts] tell us and if they say we shouldn't risk it we'll travel tomorrow or the day after," said Barcelona coach Pep Guardiola. 
 
 During last April's six-day shutdown only a handful of flights took off or landed in the UK. 
 
 Thousands of Britons found themselves stranded overseas forcing many to make long and expensive journeys home by land. Airlines estimated the shutdown cost them $1.7bn (£1.1bn). 
 
 The CAA said ash levels would now be graded as low, medium or high, and airlines would be notified if levels reached medium or high. 
 
 Airlines would then consider whether to fly, according to risk assessments already carried out, the CAA added. 
 
 The Foreign Office is advising passengers to remain in regular contact with their travel agent or airline for the latest news on the status of flights and bookings. 
 
 The Grimsvotn volcano in Vatnajokull National Park began erupting on Saturday with ash rising to 20km (12 miles) but, although still active, is now not as powerful with a plume of 13km (8 miles). 
 
 Iceland's airspace has been closed for a period as a result. 
 
 Ash from the volcano, which is 60 miles (97km) from the nearest human settlements, has settled over farmland and livestock, causing difficulties for some farmers and tourists have been evacuated from the country's main national parks. 
 
 The Grimsvotn volcano lies beneath the ice of the uninhabited Vatnajokull glacier in south-east Iceland. The latest eruption is its most powerful eruption in 100 years. 
 
 Experts say this eruption is on a different scale to the one last year and ash particles are larger and, as a result, fall to the ground more quickly. ||||| The spread of dense ash from the erupting Iceland volcano could force the cancellation of up to 500 commercial flights in Northern Ireland, Scotland and parts of Scandinavia, the European air traffic agency said Tuesday. 
 
 Passengers rest on the floor as their flights have been canceled at Edinburgh Airport in Edinburgh, Scotland Tuesday, May 24, 2011. A dense ash cloud from an Icelandic volcano blew toward Scotland, causing... (Associated Press) 
 
 A departures board shows canceled flights as the airport remains open with limited flights at Edinburgh Airport in Edinburgh, Scotland Tuesday, May 24, 2011. A dense ash cloud from an Icelandic volcano... (Associated Press) 
 
 Passengers rest on the floor as their flights have been canceled at Edinburgh Airport in Edinburgh, Scotland Tuesday, May 24, 2011. A dense ash cloud from an Icelandic volcano blew toward Scotland, causing... (Associated Press) 
 
 Passengers rest as their flights have been canceled at Edinburgh Airport in Edinburgh, Scotland Tuesday, May 24, 2011. A dense ash cloud from an Icelandic volcano blew toward Scotland, causing airlines... (Associated Press) 
 
 Passengers rest on the floor as their flights have been canceled at Edinburgh Airport in Edinburgh, Scotland Tuesday, May 24, 2011. A dense ash cloud from an Icelandic volcano blew toward Scotland, causing... (Associated Press) 
 
 Between 200 and 250 flights had already been canceled, said Brian Flynn, head of network operations at Eurocontrol. There are just over 30,000 flights within Europe on average every day at this time of the year. 
 
 Ash from the Grimsvotn volcano already forced President Barack Obama to shorten a visit to Ireland, and has raised fears of a repeat of huge travel disruptions in Europe last year when ash from the Eyjafjalljokull volcano stranded millions of passengers. 
 
 Flynn said he did not expect Obama's European tour to be further affected and authorities have said they don't expect the kind of massive grounding of flights that followed last year's eruption. They say procedures have been improved since then and the cloud is currently not expected to move over continental Europe. 
 
 The British Civil Aviation Authority said strong winds over Scotland was making it hard to predict the direction in which the ash would move, but air traffic controllers said it would reach airports in Scotland, northern England and Northern Ireland on Tuesday afternoon. 
 
 British Airways suspended all its flights for Tuesday morning between London and Scotland, while Dutch carrier KLM and Easyjet canceled flights to and from Scotland and northern England at the same time. Three domestic airlines also announced flight disruptions. 
 
 National Air Traffic Services, the agency that controls air traffic over Britain and the eastern Atlantic, said airports will remain open but flights will be affected between 1:00 p.m. (1200GMT) and 7 p.m. (1800GMT) local time. 
 
 NATS said in a statement that the ash will affect airports in Londonderry in Northern Ireland, Glasgow, Edinburgh and Prestwick in Scotland, and Newcastle, Carlisle, Durham Tees Valley and Cumbernauld in northern England. It advised passengers to check with their airlines before travelling. 
 
 Budget airline Ryanair said it did not believe there was a need to cancel all flights between Ireland and Scotland, and said it would meet with regulators Tuesday morning to discuss the issue. 
 
 Norwegian airport operator Avinor said the ash cloud that swept over southwestern Norway earlier Tuesday has now moved away from the coast and no longer affects the airports in Stavanger and Karmoey. However, it said the ash is expected to return to southern Norway in the afternoon.
– The volcanic ash cloud drifting from Iceland toward Europe has already caused more than 250 flights to be canceled, and that number could rise to 500, according to the European air traffic agency. Clouds have already affected Iceland and Scotland and could reach northern Europe within 48 hours, the Wall Street Journal reports. Northern Ireland, northern England, Scotland, and parts of Scandinavia could be affected. Even so, the groundings are not expected to reach the level they did after last year’s Eyjafjalljokull eruption. Although President Obama was forced to shorten his visit to Ireland due to the ash cloud, the AP reports that an official does not expect the rest of his European tour to be affected. Meanwhile, crazy airline Ryanair (remember this?) called on air traffic controllers today to reopen airspace over Scotland, since the company did a verification flight and believes it is safe. The BBC has a list of airlines that have canceled flights, and notes that service is expected to be mostly back to normal by tomorrow.