A deserted Belfast airport and latest pictures of the angry volcano (1 May)

All flights in and out of Northern Ireland and the Irish Republic will resume at 1300 BST after being grounded owing to a fresh volcanic ash threat.

Services to and from Northern Ireland and the Republic were cancelled from 0700 BST by aviation authorities.

Airspace over Scotland's Outer Hebrides has been closed, with Tiree, Barra and Benbecula airports as well as Campbeltown in Argyll shut down.

Ash is drifting from the same Icelandic volcano that disrupted 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. Our decision to close earlier today was based solely on the safety risks to crews and passengers

Irish Aviation Authority statement
How chaos unfolded: in graphics
Ash cloud alert for Scottish routes
All Northern Ireland airspace closed
EU to discuss ash crisis lessons
The IAA (Irish Aviation Authority) said it had cleared Irish airports to open for full operations from 1300 BST and Dublin, Shannon, Cork, Knock, Donegal, Waterford and Kerry could resume normal operations.

It added that flights from the UK and continental Europe flying across the airspace would not be affected.

And in the UK, the Civil Aviation Authority said all Northern Ireland airspace would be closed from 0700 BST until 1300 BST with Belfast International, Belfast City and City of Derry airports all affected.

The ban disrupted the plans of Conservative leader David Cameron, who had been due to make his first campaign visit to Northern Ireland.

Mr Cameron is now expected to make the journey by helicopter.

Earlier, the CAA closed airspace over Scotland's Outer Hebrides from 1800 BST on Monday, disrupting flights to and from Barra and Benbecula.

Highlands and Islands Airports Ltd said flights to and from Tiree and Campbeltown were also suspended.

In a statement, the CAA said the decision followed consultation with the UK Met Office and Nats, the air traffic control service.

It said airspace had been closed because ash concentrations exceeded the levels agreed as safe by engine manufacturers.

Liam Dutton of the BBC Weather Centre said the concentration of ash was expected to become thinner by the middle part of the day.

In a statement, the IAA said winds from the north could cause further problems later in the week.

“Our decision to close earlier today was based solely on the safety risks to crews and passengers as a result of the drift south of the volcanic ash cloud caused by the north-easterly winds,” it added.

Irish Ferries said it had space on services between Ireland and the UK as well as Ireland and France.

Hundreds of flights have been affected:
All Aer Lingus flights to and from Dublin, Cork Shannon and Belfast airports to the UK and Europe scheduled before 1300 BST have been cancelled. Most transatlantic flights will operate.

All Ryanair flights into and out of the Irish Republic and Belfast in Northern Ireland until 1400 BST have been cancelled. Ryanair's Stephen McNamara said he was “confident” services would resume after that time

Aer Arann services to and from Derry and Donegal airports were cancelled on Monday night

EasyJet warned flights departing from Scotland and Northern Ireland on Tuesday could face disruption

BAA, which operates six UK airports including Heathrow, Stansted and Glasgow, is advising passengers heading for Ireland to contact their airlines for advice.