European flights to and from the Republic and Northern Ireland are due to resume following the disruption caused by the Icelandic volcano.
Flights were disrupted earlier because of ash from the Icelandic volcano, RTE has reported.
The IAA took the decision after reviewing the movement of the ash plume.
The UK's Civil Aviation Authority said flights to and from Northern Ireland would be able to start again from 1pm.
Airports in both the Republic and Northern Ireland had been affected.
Passengers are still advised to check airline websites.
Speaking on RTÉ Radio, the Chief Executive of the IAA, Eamonn Brennan, said that the threat of travel disruption would remain for a number of months.
Airports affected include Dublin, Cork, Shannon, Kerry, Knock, Donegal, Sligo, Belfast International, Belfast City and City of Derry.
Aer Lingus has confirmed all its UK and European flights into and out of Dublin, Cork, Shannon and Belfast airports prior to 1pm this afternoon have been cancelled.
The airline said it plans to operate all its flights to the US, with the exception of EI 105 from Dublin to New York.
Ryanair has cancelled all its flights into and out of Irish airports and Belfast airports from 6am until 2pm.
Over-flights of Ireland from the UK and Europe have not been impacted and are operating normally.