The ash is back. Fresh volcanic activity under the Eyjafjallajokull glacier in Iceland has resulted in a fresh ash plume being pushed about 5.5km (18,000ft) into the air.
Airports in parts of Scotland and Northern Ireland closed from 0700 BST because of risks from volcanic ash, the Civil Aviation Authority has said.
Glasgow, Prestwick and Derry are likely to be closed all day, while there are plans to shut Inverness in the morning only, and Belfast in the afternoon.
The CAA advised air passengers to check with airports before travelling and warned the situation was changeable.
Last month, volcanic ash clouds from Iceland grounded flights for six days.
The situation in the skies has been changing hour by hour, meaning the picture for air travellers is unclear.
Dublin Airport will also close from 1100 BST until further notice.
Forecasts show the 60 nautical mile buffer zone imposed around high concentrations of ash is close to some northern airports.
Belfast International 1300-1900
Belfast City 1300-1900
All times in BST. Source: CAA at 0200 BST
However, the latest advice issued by the CAA at 0200 BST said airports in Edinburgh and north-west England could safely stay open on Wednesday, despite the proximity of the ash.
The CAA says the South East of England is unlikely to be affected on Wednesday.
In a statement, the CAA said: "The situation remains changeable, so passengers expecting to travel from airports in Scotland, Northern Ireland, the North of England and north Wales should contact their airlines to check whether their flight is operating."
All flights in and out of Northern Ireland and the Irish Republic have been grounded since 0700 BST because of fresh risks from volcanic ash.
Airspace over Scotland's Outer Hebrides was closed, affecting Tiree, Barra and Benbecula airports, with Campeltown in Argyll also closed.
Flights in and out of the Republic are due to resume from 1300 BST.
An ash plume is drifting south from the same Icelandic volcano that wreaked havoc to European air travel in April.
Flights over Europe were banned for six days last month because of fears of the effect of volcanic ash on plane engines.
In the rest of the UK, schedules are operating as normal.
The decision to lift the restrictions followed safety tests that showed the engines could cope in areas of low density ash.
The fresh disruption comes as European Union transport ministers are meeting in Brussels to discuss ways to improve air traffic management in the wake of last month's events.
Last week a spokeswoman for EU Transport Commissioner Siim Kallas said that had there been more co-ordination at EU level, air traffic could have resumed up to three days earlier.
Happy St Patrics Day Everyone!
As millions of people all around the world prepare to celebrate Irelands most famous Saint here are a few interesting facts about St Patricks Day;
St. Patrick is the patron saint of Ireland, although he was born in Britain, around 385AD. His parents Calpurnius and Conchessa were Roman citizens living in either Scotland or Wales, according to different versions of his story.
Until the 1970s, St. Patrick's Day in Ireland was a minor religious holiday. A priest would acknowledge the feast day, and families would celebrate with a big meal, but that was about it.
On any given day 5.5 million pints of Guinness, the famous Irish stout, are consumed around the world. On St. Patrick's Day, that number more than doubles to 13 million pints, said Beth Davies Ryan, global corporate relations director of Guinness.
The St. Patrick mythology includes the claim that he banished snakes from Ireland.
Birmingham holds the largest Saint Patrick's Day parade in Britain, which is said to be the third biggest parade in the world after Dublin and New York.
The first St. Patrick's Day parade took place not in Ireland, but in America, when Irish soldiers serving in the English military marched through New York City on March 17, 1762.
But Dont be fooled into thinking that St Patricks day is all Irelands is about. A holiday in Ireland allows one to experience a culture deeply steeped in history. Ireland's history is reflected in the warm hospitality, underrated delicious traditional Irish food and drink, brilliant Irish folk music, and beautiful landscape. Whether enjoying a morning breakfast at a guest house in Dublin, downing a pint or two in a pub in Belfast, experiencing the local artists of Kerry or Cork, or hiking along a seaside cliff on the Dingle Peninsula, it is hard not to feel a part of the dramatic culture of the country's people and the rich history that is Ireland.
Why not search Bargain Villas for your next Ireland Holiday Villa