Services in and out of Shannon and Cork airports have resumed following a radar failure in the west of Ireland on Tuesday night.
The Irish Aviation Authority (IAA) said it had switched to a back-up system and lifted restrictions.
Several flights had been cancelled and temporarily diverted as a result of the disruption.
Those using Dublin airport were not affected.
In a statement just before 11pm, the IA said a "technical issue occurred with the Shannon ATC system".
“Safety is the IAA’s main priority and in accordance with normal procedure the IAA restricted air traffic while the issue was being investigated.”
After switching to the back-up system, it said “traffic flows are now in the process of being restored to normal capacity”.
An investigation is ongoing and despite restrictions having been lifted, those intending on flying from either airport are advised to check in with their airlines.
In an earlier tweet, Cork Airport had said a “radar problem in the west of Ireland which covers airspace including Cork Airport is impacting all flights coming from the west/south of Ireland”.
“Anything already in the airspace was processed through or has landed but nothing else is allowed to enter this airspace at present.”
Shannon Airport had similarly tweeted: "Air Traffic Control at Ballycasey, Shannon are experiencing issues with their flight radar. Work under way to rectify the situation. Arrivals and Departures at SNN have been suspended until the radar is fully operational."
Shannon Airport has said Aer Lingus flight EI 387 from London Heathrow and Ryanair flight FR3326 from Krakow have both landed there. Earlier it had said the flights would divert to Dublin.
Aer Lingus earlier said the following four services had been cancelled:
EI912 Knock to London Gatwick.
EI249 London Gatwick to Dublin.
EI724 Cork to London Heathrow.
EI725 London Heathrow to Cork.
An Aer Lingus spokeswoman said ground staff is providing those affected with hotel accommodation as required.
Those scheduled to fly tonight are advised to check aerlingus.com prior to departing for airports.
