The Irish Aviation Authority has said Irish airspace is to close at midday and will remain closed until 8pm tonight causing major disruption for thousands of people.
A cloud of ash caused by a volcano erupting in Iceland has brought havoc to flight schedules across Ireland, the UK and Europe.
The Dublin Airport Authority has said 450 flights in and out of Ireland have been cancelled today, affecting almost 60,000 people.
Flights out of Dublin, Cork, Shannon and Belfast to cities across the UK as well as Amsterdam, Brussels and Munich have been affected with Aer Lingus cancelling flights - some transatlantic flights will operate as scheduled.
Ryanair axed flights in and out of Dublin and Cork to the UK, Norway, Sweden and Denmark.
The situation is to be reviewed throughout the day but cancellations and delays are expected to continue into tomorrow.