An investigation has started into a technical issue that disrupted flights in Ireland on Tuesday evening.
There were cancellations from Shannon and Cork airports following the fault with the air traffic control (ATC) system in Shannon.
Inbound flights faced cancellation or delays of up to three hours when traffic flow was disrupted because of the fault.
A number of flights due to land at Shannon were diverted to Dublin Airport.
The Irish Aviation Authority (IAA) confirmed just before 11pm on Tuesday that flight restrictions had been lifted.
It said: "Earlier this evening a technical issue occurred with the Shannon ATC system. Flights to and from Shannon and Cork were affected by the restriction. Dublin was not affected.
"As part of planned contingency, the IAA moved to its back-up systems and the flight restrictions have been lifted.
"Traffic flows are now in the process of being restored to normal capacity. Flights are now operating again to and from Shannon and Cork.
"An investigation into the technical issue is ongoing. Intending passengers should check with their airlines."
Cork Airport said on Twitter: "Flights have resumed @CorkAirport following activation of a back up system by the IAA. The last scheduled departure to London Stansted with Ryanair has taken off and further arrivals are due presently. Most flights are now expected to operate to schedule on Wednesday morning."
Shannon Airport tweeted: "Thanks to all passengers for their patience & to all our colleagues for their help & support."