Up to 3,500 passengers at Dublin airport were affected by the cancellation of 18 flights to Britain as a result of the security alert at London Heathrow.
The Dublin Airport Authority said that at one stage hundreds of passengers were queuing in the terminal building to seek refunds or to reschedule flights.
Passengers told The Irish Times that they had queued for up to three hours to reach airline desks to make new arrangements.
Some sought to rebook their tickets online from internet terminals in the arrivals halls. Queues at the Aer Lingus, Ryanair and BMI desks had largely subsided by early afternoon.
The airport authority said that 18 outbound flights had been cancelled as were a further 18 inbound flights. The cancellations largely affected passengers travelling to London while there were delays of about an hour to other parts of Britain. Flights to London began resuming in mid-afternoon.
Dublin Airport Authority said that no new general restrictions on hand baggage, similar to the measures put in place in London, were being imposed in Ireland. The issue of baggage allowed into aircraft cabins was one for individual airlines.
However, travellers to the US faced a ban on duty-free purchases. The request not to sell alcohol or perfume to passengers travelling to the US had been made to airlines by the Department of Homeland Security in the United States.
An airport authority spokeswoman said the ban appeared to be open-ended.
However Aer Lingus said yesterday that it would be able to offer liquid refreshments to passengers on its transatlantic routes and that its catering supplies went through a strict security system.
Once it become aware of the security alert in London early yesterday, the Dublin Airport Authority deployed a special task force for tackling congestion in the terminal.
It established corrals to separate passengers for London queuing at airline ticket offices from those seeking to check in baggage for other destinations. Queuing passengers were given bottled water as they waited.
Dick Butler, Aer Lingus director of ground operations at Dublin airport, said the airline had cancelled 20 flights to Heathrow from Dublin, Cork and Shannon, affecting more than 3,000 passengers. All were offered their money back or a new booking.
BMI cancelled two flights in each direction between Dublin and Heathrow, while others had experienced delays of two to three hours. It said that all affected passengers had been rescheduled on later flights.
BMI warned that there could be further disruptions to services from Heathrow today due to the heightened security measures and that these could lead to knock-on delays on some services from Dublin.
Ryanair cancelled 14 flights between Dublin and Britain, with four other flights to or from the Republic cancelled.
Vivienne Dowman from Dublin, travelling to London with her mother for a funeral, said she had waited nearly three hours to make new arrangements with Ryanair. She praised the airport authority for providing water and a wheelchair for her mother.
By mid-afternoon much of the media focus at Dublin Airport had shifted from those waiting to depart to those arriving back from Heathrow.
Aisling Hourican from Dublin said there were just "queues, queues and TV crews" but people were quite calm.
Shireen Rountree from Wicklow said the queues were "like Christmas Eve".
"There was really strict security," she said. "They took everything. You could not even bring a bottle of water."
Barry Corcoran from Blackrock, Dublin, said most people had been fairly relaxed, but that "some guys in the queue were fairly stressed that they were missing their golf".