Aer Lingus has cancelled 12 flights between Ireland and Scotland tomorrow because of Iceland's volcanic ash cloud.
A number of flights to and from Edinburgh, Glasgow and Aberdeen from Dublin, Shannon and Cork have been affected.
Passengers advised to check their website for details on how to change their flights or apply for a refund.
British Airways has also cancelled all planned services between London and Scotland tomorrow because of the threat.
The Irish Aviation Authority said that flights to and from Ireland could be disrupted later this week from an ash cloud billowing from the volcano.
The Irish Aviation Authority are continuing to say no disruptions to flights are expected in Irish airspace in the next 24 hours.
A spokesperson said they are still monitoring the situation and should it deteriorate updates will be made available on their website.
In the meantime, passengers are being advised to also check the website of their airline.
IAA's senior aviation executive Martin Towey has said that 'we do not believe that there will be any kind of disruption in the next 48 hours.'
Martin Towey has said that 'there could possibly be some disruption towards the end of the week.'
Met Éireann meteorologist Pat Clarke has said that the ash cloud is expected in Irish airspace by tonight.
A spokeswoman for EU transport commissioner Siim Kallas has suggested that the picture was less certain.
Siim Kallas has said that 'there is at the moment a possibility of volcanic ash affecting the European airspace starting with the northwestern areas like the UK and Ireland possibly today or tomorrow.'
The eruption by Iceland's most active volcano is set to keep the island's main airport closed.
Experts say there is little chance of a repeat of last year's six-day closure of airspace which also hit trans-Atlantic flights, although airlines have been warned the new ash cloud will drift.
So far Iceland, particularly the towns and villages to the south and east of the Grimsvotn volcano, have been hit worst as a thick cloud of ash descends on the area, smothering cars and buildings.
Last night, the cloud began to drift over the capital Reykjavik.
Iceland's meteorological office have said that the plume from Grimsvotn, which last exploded in 2004, has fallen to around 15km in height from a peak of 25km.
But the eruption is much stronger than the one at a volcano further south last year which closed European airspace and halted trans-Atlantic flights, due to worries that particles could get into aircraft engines and cause accidents.
The airline industry has said it lost €1.2bn in revenue last year.
Icelandair stopped flights yesterday and said on its website the halt could continue today. It said 6,000 passengers had been affected by cancellations so far.
Ryanair's deputy CEO Michael Cawley said he was certain there would be no disruption to flights this time and described last year's volcanic ash crisis as an 'overreaction'.
Meanwhile, US President Barack Obama has moved forward his departure to fly out of Dublin to tonight at 7.30pm due to the threat to flights from the Icelandic ash cloud.
Earlier, the European Aviation Crisis Coordination Cell held a meeting to bring together all the major players.
Further information: Volcanic Ash Advisory Centre|Irish Aviation Authority|Met Éireann|British Met Office