The Irish Aviation Authority (IAA) closed the country's airspace today with volcanic ash from Iceland causing more chaos.
The flight restrictions, imposed from 7am local time, are set to stay in place until 1pm IST today.
Dublin, Shannon, Cork, Knock, Donegal, Waterford, Kerry, Galway and Sligo airports are all affected.
Transatlantic flights are operating as normal due to new jet-engine tolerance levels that allow aeroplanes to fly over the volcanic ash cloud.
The IAA said the decision was entirely based in the safety of crews and passengers, and the situation will be reviewed as the week goes on.
The closures follow weeks of disruption after volcanic ash clouds sparked safety fears on 15 April closing airports across western and northern Europe, and leaving hundreds of thousands of travellers stranded.