No further disruption is expected at Irish airports over the next 48 hours as the ash cloud caused by the Eyjafjallajökull volcano has moved out of Ireland's airspace.
The Irish Aviation Authority (IAA) said the outlook for the coming days was positive and it did not anticipate any further restrictions over the next two days.
It said intending passengers should continue to check for flight disruption with airlines.
"The volcanic ash cloud is moving east, away from Irish airspace and, based on the meteorological situation, the IAA does not anticipate putting any further restrictions in place due to volcanic ash for at least the next 48 hours," it said.
Disruption is expected to be reduced even further tomorrow following a decision by the UK's Civil Aviation Authority to adapt measures that would minimise the cancellation of flights by volcanic ash clouds.
The CAA said a Time Limited Zone had been agreed, in which it will be safe to allow flights for a limited time at higher ash densities than are currently allowed.
To operate in the new zone, airlines need to present the CAA with a safety case that includes the agreement of their aircraft and engine manufacturers. UK airline Flybe is the first to achieve this and will be able to use the new zone from midday tomorrow.
The measures will be introduced from midday tomorrow.
The announcement followed another day of disrupted air travel, with Dublin airport was the worst-affected. Some 300 flights in and out of the facility were cancelled last night and this morning, affecting the travel plans of some 36,000 people.
Airport authorities said Dublin, Cork and Shannon were now operating as normal, while airports in Donegal, Sligo, Belfast, Galway and Knock have also reopened and were operating normal services.
The CAA said this meant that areas of UK airspace that would have previously been closed can safely open, further minimising flight disruption.
Aer Lingus said today it had been forced to cancel all flights with a scheduled departure time up to 12 midday due to the airspace restrictions.
However, the airline said it would resume a full schedule of flights from Dublin, Cork and Shannon from midday and from Belfast after 1pm.
Due to the restrictions, a number of Aer Lingus flights to and from London Gatwick to Cork and Malaga were cancelled earlier, it said.
Ryanair said today it had scheduled extra flights from Dublin, East Midlands, Glasgow Prestwick and Liverpool flights to/from Alicante, Canary Islands and Faro, and additional services between Dublin and London Stansted from tomorrow which disrupted passengers can now transfer to.
Volcanic ash grounded 1,000 flights and delayed hundreds of thousands of passengers in parts of northern Europe today.
Several of Europe's busiest airports, including London's Heathrow and Schiphol in Amsterdam, were closed for several hours due to fears the ash could damage jet engines and bring down aircraft.
Eurocontrol, the European air traffic agency, said about 1,000 flights out of a total of 28,000 in Europe had been cancelled today.
London's Heathrow and Gatwick airports reopened after overnight closures, but passengers were warned to expect long delays and cancellations through the day.
British flights face further disruption tomorrow when British Airways cabin crew are due to strike in a long-running dispute over pay and working practices.
The IAA announced the extension of airspace closure late yesterday after earlier imposing restrictions on a number of airports.
The IAA said the move came after extensive observations of the drift of the ash cloud. Volcanic activity and the latest weather forecasts indicated “an increased quantity of ash over Irish airspace”.
The latest closures came after northwesterly winds pushed high concentrations of ash from the Eyjafjallajökull volcano southeastwards from Iceland.
Dublin Airport Authority spokeswoman Siobhán Moore said passengers whose flights had been cancelled should not travel to the airport, but should contact airlines instead.
Those with reservations for flights that have not been cancelled are advised to come to the airport on time. Delays are expected, however, as not all aircraft may be in place, and airlines may have to focus on positioning aircraft and crews.
The economic effect of the disruption was highlighted last week when figures released by the IAA revealed that 4,743 flights to and from Ireland were cancelled during the April 15th-May 10th period at a cost of €8 million to the authority.
In Europe, 104,000 flights were cancelled.
The International Air Transport Association (IATA) has estimated that airlines, already battered by the global economic downturn, lost €1.5 billion during April alone after more than 100,000 flights were cancelled across the continent.