Northern Ireland airspace will close from 7am this morning as ash from the Icelandic volcanic cloud has returned.
The Civil Aviation Authority (CAA) said Belfast International, Belfast City and City of Derry airports will all be closed until further notice.
All flights in and out of the Republic will also be grounded after the the Irish Aviation Authority (IAA) revealed restrictions will be imposed from 7am to 1pm as a dense plume travels across the island.
The authority said the decision to ground aircraft was based on the safety risks to crews and passengers as a result of the drift south of the volcanic ash cloud caused by the north-easterly winds.
It maintained the Republic falls within the predicted area of ash concentrations that exceed acceptable engine manufacturer tolerance levels.
"Current information from the Volcanic Ash Advice Centre (VAAC) suggests that a no-fly zone will have to be imposed over Ireland tomorrow that will affect Dublin, Shannon Galway, Sligo, Ireland West (Knock), Donegal, Cork and Kerry," said a spokesman.
"No flights will operate in or out of these airports until at least 1300hrs local tomorrow," he added.
The IAA said over-flights of Ireland from the UK and Europe will not be impacted tomorrow with flights in mainland Europe operating normally.
Almost 440 flights were due to depart and fly into Dublin Airport throughout the day, with more from Shannon and Cork in the south of the country and Ireland's smaller regional airports.
Ryanair and Aer Lingus have warned passengers they face disruptions, with delays and possible cancellations.
Elsewhere Aer Arann has already been forced to cancel tonight's services to and from Derry and Donegal airports and a flight from Donegal to Dublin in the morning.
"Passengers are advised not to travel to their departure airport if their flight has been cancelled," said the company in a statement.
The IAA advised all passengers intending to travel to check each airline's website.
Hundreds of thousands of travellers were left stranded last month when European airspace was closed for almost a week after eruptions from Icelandic volcano Eyjafjallajokull.
Eamon Brennan, IAA chief executive, said even though emissions from the volcano have been low over the last number of days, a north-easterly wind pushed the plume over Ireland and the Scottish Isles.
He said that based on the new regime imposed in Europe last week, officials had no choice but to impose a no-fly zone and a 60-mile buffer zone which would effectively close Shannon and Dublin airports.
"What's unusual about this is that we are the country affected in Europe, it may affect parts of Scotland later in the day," he said.
"Ireland will be closed for business from 7am."
Mr Brennan said the problem with the cloud is that the density levels are quite high.
"We are quite optimistic that it will dissipate and we are quite optimistic for Dublin and for Shannon tomorrow afternoon but we will make a reassessment for that in the morning."