The Irish Aviation Authority has warned that the disruption to flights from the volcanic ash cloud could last days.
It comes as the authority announced the closure of Dublin Airport at midday today, causing travel chaos for thousands of air passengers
The decision to cancel flights in airports across Ireland, Europe and the UK has been taken for safety reasons as volcanic ash can damage aircraft engines.
Director of Operations with the Irish Aviation Authority Donie Mooney, says he's expecting an update from the Volcanic Ash Advisory Centre at 1pm this afternoon.
The Irish Travel Agents Association is warning people who have booked long-haul holidays online that they could lose out because of today's disruption.
Tour Operators and individual airlines will do their best to reschedule flights that have been cancelled but passengers who miss connecting flights may not be compensated unless they have insurance.
Volcanic ash from Iceland has moved closer to Irish airspace, prompting the decision to close operations in Dublin.
The decision has been made based on advise from the Volcanic Ash advisory Centre in London.
Thousands of passengers have been affected by the 450 flight cancellations.